Talk:Mole (unit)/Archive 1

Archive 1

Archive 2

Etymology

why is it called a mole??—Preceding unsigned comment added by 24.49.80.29 (talk • contribs) 03:19, 22 October 2002 (UTC)

Particle

I thought I'd link the "particle" to a relevant article but I could only find particle which is generic, particle physics which isn't very relevant, and subatomic particle which at first seemed to fit but turns out not to after all. The current text is using "particle" in a sense that seems to be narrow and technical but explicitly includes atoms and molecules. Is the term just being used generically to mean something like "small speck," or is there a more precise definition for "particle" when used in this chemical sense? 24.80.122.19 06:41, 14 April 2004 (UTC)

Particle is a general statement in Chemistry. You use it in explanations when what you're referring to are atoms or molecules and whatnot. This is because both the terms atom and molecule are themselves specific. An atom is one individual atom (eg. Mg or Na just there by themself) and a molecule refers to a substance that contains several atoms in it, eg. Glucose (C6H12O6).

So when you're talking about the mole you use the term particle in the explanation because moles are applicable to more than one thing.

Yes, congratulations, you have finally ascertained why it's a dimensionless quantity. You get a ph.d.

Half a mole?

The mole makes it easier to interpret chemical equations in practical terms. Thus the equation:

   2H2 + O2 = 2H2O

can be understood as "two moles of hydrogen plus one mole of oxygen yields two moles of water."

2H₂, that wouldn't be 4 moles of Hydrogen atoms?

No, because "hydrogen" is referring to hydrogen gas, which is H₂, not atomic hydrogen. There are some logical reasons to avoid using half-moles (specifically, the reaction H₂ + ¹/₂O₂ implies that two hydrogen atoms interact with an oxygen atom, which of course doesn't happen), but they are often useful. Ckerr 18:49, 22 July 2006 (UTC)

From my knowledge (I'm still in High School chemistry though) it is incorrect use a value of 3.5 (or anything but a whole number) when dealing with the coeffecients in a chemical formula. Did my teacher just explain it this way to simplify it?

It isn't incorrect. I'm used to see formulas like H₂ + ¹/₂O₂ -> H₂O. But neither is it very common.

I'm in the same situation as you, I am being taught "NO DECIMALS!!!! WHOLE NUMBERS ONLY!!!!!" But I think that for theoretical formulas that aren't telling you what chemicals to add, it's okay, because if you're trying to explain the properties of element X, it would be easier to understand "X + .5O + .33H + .2C--> [random compound]" rather than doing "30X + 15O + 10H + 6C--> 30[random compound]" which is the closest whole-number form of the first equation. Twilight Realm 03:34, 11 October 2005 (UTC)

There is a such thing as half of a mole, or basically any part of a mole. The only reason that teachers discourage the use of fractions of moles is that they also apply the same equations you will be using at the atomic scale, where you have the number of atoms listed in the equations. Its possible to have 0.5 a mole of oxygen atoms in an equation, but impossible to have half of an oxygen atom in an equation, so teachers discourage the use of part moles for the ability to discuss more topics easier with the class. Zack 01:43, 24 January 2006

Fractional mole values may be avoided for pedagogical purposes, but mole fractions are used all the time (in fact unavoidable) in the field of chemical engineering. --Blainster 21:26, 24 January 2006 (UTC)

The material balance equations are usually written in terms of the key component that is being considered. If you are most conserned with the hydrogen, then the oxygen will be 0.5 in quantity. Ifyou are most concerned with the oxygen, then the hydrogen and water will be 2 in quantity. - BeastRHIT 06:25, 9 July 2006 (UTC)

.012 kg?

Why does the article use the term ".012 kg"? Wouldn't it be more logical to state that as "12 g"? Nik42 08:54, 26 January 2005 (UTC)

• Probably because the author wants to express this quantity in another SI base unit, the kilogram, rather than a derived unit like the gram. –Peter J. Acklam 07:13, 7 February 2005 (UTC)
  • Ah, right, one of the oddities of the metric system ... the prefix-less form is derived from the prefixed form ... :-) Nik42 04:46, 9 February 2005 (UTC)
    • Regardless of what the author might have wanted I agree that it would still be more logical to state it as 12 grams. Easier to read too. I'm changing it. Jimp 30Sep05

"The author" was the CGPM, which used that terminology in its semiofficial English version of resolution officialy defining the unit, and in the offical French version too with French spelling of unit and comma decimal point. It is followed by the BIPM in its SI brochure, and by NIST in SP 811. Well, all of them, as this article did too, actually use the leading zero before the decimal fraction. Nonetheless, I agree that it should be "12 grams". Gene Nygaard 08:49, 30 September 2005 (UTC)

Examples

Wikipedia is better than a normal encyclopedia for many reasons. One of them is that it is easy to understand for the normal person (as it is written and/or edited by normal people). Let's help keep it comprehensible. Avogadro's number, the number which the whole concept of the mole is based upon, is big. Really really big. Enormously big. Way too big to actually comprehend. But we can get an idea of it with some good examples, which also make the article a bit more interesting. 10²³, like I said, is unbeleviably huge, but if you don't already know about it, it's just a couple of numbers.

Anyway, my chemistry textbook has two examples to help comprehend the size of the number. The first one is that if you took a mole of sand, it would cover the city of Los Angeles (or something) in 600 meters of sand. The second example is that if you had a mole of rice, it would weigh as much as a million cars for every person on earth. Now, when you read these, you are probabably amazed by how much that is, but you don't get any farther than that. You don't actually get a grasp on how big it is, just that it's really really big. A million cars for every person on earth? No idea how much that is. If, however, you modified the first example, it would work. Get a picture of a single grain of sand among many, show how small it is. Then, get a picture of the city of Los Angeles or whatever it is, an aerial view, and show how much 600 meters would be. That would help a lot.

I'm willing to help, in fact I'll put together the picture, if people agree with me, and if someone can do the calculations to verify the facts (I may have remembered the specifics wrong). Twilight Realm 03:19, 11 October 2005 (UTC)

I haven't done the calculation, but I remember it to the effect of "a mole of sand grains (or maybe rice) would cover Earth a few meters deep." The problem with this is, 'who can actually understand and appreciate the size of Earth?' - BeastRHIT 06:34, 9 July 2006 (UTC)

Avogadro's Number is very big, but it doesn't even come close to googol.--Jack 02:10, 11 October 2006 (UTC)

Then what ARE the units????

Okay, so if mole is not a dimensionless quantity (and I found at least one physics discussion list where it was called such), then what *are* the units? The problem is this: it makes no sense to say you have "one mole of something" you have "one mole of molecules" or "one mole of atoms". Say you have water. Each molecules has 3 atoms. Now, I could say I have "3 moles of water" when I mean "3 moles of atoms of water" or I could say "1 mole of water" when I mean "1 mole of molecules of water. The point is, the unit has no meaning until you specify whether you mean atoms, or molecules, or whatever. That is precisely what a dimensionless quantity is. If it were not, then "1 mole of water" would be "1 mole of water", regardless of whether you picked molecules or atoms. "Amount of substance" is just another way of saying "this many". The fact that you even mentioned the example of "a mole of grains of sand" perfectly illustrates what's going on. So, the units could be not only molecules, or atoms, they could even be grains of sand! In fact, they could be chairs, or windmills, or nations, or ideas. They could be anything at all. This is same thing as realising that "amount of substance" is just a dimensionless quantity which says "take this many of whatever". That is not a unit.

Okay, the example with water isn't the best. The point remains, even if you restrict yourself to so-called "elementary elements", you still get different units depending on what you're measuring. if you measure water, you measure molecules; if you measure hydrogen atoms, you measure atoms. Still, the type of elementary element should remain invariant from measurement to measurement for a "mole" to have any kind of dimensional unit. Otherwise, you end up with nonsense, like

H2 + 0 --> H20

2 moles of hydrogen + one mole of oxygen gives 3 moles of H20. This is what happens when you remain consistent throughout usage (which is what dimensional quantities should do.)

Just to be clear, in every other truly dimensional quantity you think of, when you take 2 of that unit, and add 1 more unit to it, you get 3 of that unit (2 grams + 1 gram = 3 grams; 2 seconds + 1 second = 3 seconds). The mole seems to be the only "dimensional unit" that disobeys that principle: 2 moles (of H) + 1 mole (of O) = 1 mole (of H20). If a mole were a dimensional unit, you'd have 2 + 1 = 3, just like every other one.

Yeah. And it's 2 degrees Celsius outside the house and 18 degrees inside so if I open the windows for theose 2 degrees to come in, it will be 20 degrees here. No, most physical quantities don't add, and that's unrelated to whether they're dimensioned or not. – b_jonas 14:53, 26 March 2006 (UTC)

Portions of physics discussion list

Here are some snippets from a popular physics discussion list, populated with ph.d.'s and working astrophysicists and scientists:

Since mole is not terribly useful in astronomy, we could switch number count for mole. [1]

A mole is dimensionless, but one can still do unit analysis with moles! (same reference)

Yes, thank you Ed Shaya, who works at NASA. You hit the nail on the head -- a mole is dimensionless, yet you can still do unit analysis with it, because it's a number, i.e. 1 mole = 6.02 * 10^23 (TIMES ONE), so when you do dimensional analysis you multiply by

${\frac {\mbox{1 mole}}{6.02*10^{23}}}$

or its inverse. There are no "molecules" or "atoms" running around. If you do try to put them in and do dimensional analysis, you'll get the jibberish I discussed above.

Exhibit B

On the talk page at Mole (ordinary dab page), RitaBijlsma, a working physical chemist, says:

amount of substance does not refer to number of particles. The quantity is perfectly valid without the concept of atoms. The law of multiple proportions and law of definite proportions suffice. It is therefore more elegant to define the mole without refering to number of particles, but as a unit equivalent proportion.

In short, it's more "elegant" to define a mole as dimensionless.

Exhibit C

Mathematica, the premier mathematical computing program, treats a mole as a dimensionless quantity. Here is part of a discussion from the MathGroup Archive:

Hi Chris, as far as I remember, it is CORRECT that Mole is adimensional, saying "a Mole of atoms" is similar to saying "a dozen of atoms", a Mole is a very important number in Chemistry, but you could say "a Mole of cars", or "a Mole of computers", just like you can say "a dozen of computers". The difference is that "dozen" is a useful number in every-day life and "Mole" is a useful number in Chemistry. [2]

Definition?

1 mole is equal to 6.02* 10^23 and the units is entities per mole —The preceding unsigned comment was added by 70.25.179.34 (talk • contribs) 14:23, 25 March 2006 (UTC)

I don't think it is necessary or helpful to say:

"In other words, 1 mole = (# of atoms in 12 grams of carbon 12)/(1 atom), so that a mole is a dimensionless quantity."

The number of atoms in 12 grams of carbon 12 is 6.02 * 10^23, not 6.02 * 10^23 atoms. I think it would be better to simply say:

"In other words, 1 mole = the number of atoms in 12 grams of carbon 12, so that a mole is a dimensionless quantity." —The preceding unsigned comment was added by ArnoldReinhold (talk • contribs) 05:42, 20 October 2005 (UTC)

But the standards-keepers go to great length to make sure that this is not a "dimensionless" quantity. It has dimensions of "amount of substance", and is the base unit for that quantity.

In fact, those standards-keepers are committed to the International System of Units being a "coherent" system of units, at that term is used in metrology jargon. Thus, if this were a merely a dimensionless number, the mole could not possibly be a part of SI.

Contrast, for example, the characterization of "amount of substance" as a base quantity, and the addition of the mole as a base unit in 1971 (see CGPM for chronology), with the recharacterization of the radian and steradian not as a separate class of "supplementary units" but rather as "derived units with special names" in 1995, considered as being multiples of the quantity "one". Note that if these "units based on Avogadro's number" were considered to be pure numbers, they would also be multiples of the "quantity one". Then, since the SI is a "coherent" system, the mole could not be a part of SI at all. Gene Nygaard 22:54, 25 March 2006 (UTC)

I agree with Gene Nygaard. The official definition of the SI by the BIPM is pretty clear on which units are simply "special names for the unit one" such as radian and steradian[3][4] and which are base units of the SI, like moles[5]. The official resolution of the CGPM defining the mole makes it quite clear that it is defined as a unit, not a dimensionless quality.

Additionally I am unconvinced by the arguments that "working astrophysicists" at NASA and "working physical chemists" use the term to mean a dimensionless quality. Statements made on Wikipedia talk pages and non-peer-reviewed mailing lists are not convincing. A statement from an expert in metrology would be more convincing. An official statement from the BIPM, NIST, or other official metrological agency would be very convincing, but that is unlikely to happen as it is contrary to fact (unless the CGPM redefines mole).

Additionally one might choose to use this as evidence in the article that some researchers treat it as a dimensionless quality, but in the SI it is defined as a base unit.--Grouse 12:50, 6 July 2006 (UTC)

unit? isn't just a number?

like saying thousand? you could say "a mole of cats" right? —The preceding unsigned comment was added by 161.76.99.106 (talk • contribs) 00:25, 6 May 2006 (UTC)

That's way too many cats! But, basically yes - it is a specifically defined number or quantity in the metric system. Vsmith 13:06, 6 May 2006 (UTC)

It seems clear...

While to me, as a physicist, it seems sensible to say that the mole is unitless, it is pretty clear that the mole is defined as being dimensionful: "Note that since N(X) is dimensionless, and n(X) has the SI unit mole, the Avogadro constant has the coherent SI unit reciprocal mole." [6] That strikes me as being silly and arbitrary, and the fact that they have to state that the reciprocal mole is coherent implies that one's first thought is to assume it is incoherent. But Wikipedia is not the place to rewrite the definitions of fundamental entities, so I guess the mole really does have units. Ckerr 18:59, 22 July 2006 (UTC)

Moleonaire?

Would someone who had $6.02x10^23 be called a Moleonaire? —The preceding unsigned comment was added by 67.172.248.207 (talk • contribs) 10:43, August 14, 2006 (UTC)

That would be one major counterfeiter --Blainster 20:22, 14 August 2006 (UTC)

Changed my mind...

After some discussions with other, wiser folk at my physics department, I have decided that the mole is best described as a dimensionless unit. It is indisputably a unit--it is defined as one--but the question is whether or not it has dimension. The candidate for being a dimension is "amount of substance", as this is what a mole is defined to measure.

The argument that this is a dimensionless quantity comes from the following: 1. Numbers are dimensionless. 2. Numbers may be used to measure amounts. 3. There is no difference between the use of numbers and moles to measure amounts. Therefore, moles are dimensionless.

Premise (3) is perhaps the most flaky, but I think it can be justified as follows. If I say I have 12.044*10^23 hydrogen atoms, this is identical to the statement that I have 2 moles of hydrogen atoms. The first quantity is clearly dimensionless, since I am using only a number. Since the two statements are identical, the dimensions of the second statement must be identical to the first--and hence, the second statement is dimensionless.

Put another way, by inserting the term "moles", I do not change the dimensions of my statement, only its magnitude: the difference between "2 hydrogen atoms" and "2 moles of hydrogen atoms" is a numerical factor. By contrast, the difference between "2 hydrogen atoms" and "2 kilograms of hydrogen atoms" is a numerical factor and a dimensionful conversion factor (number of hydrogen atoms per kilogram).

Ckerr 14:56, 1 September 2006 (UTC)

Wikipedia is not a place for original research. This is official Wikipedia policy. If you wish to change the page, please provide a citation to an official statement of BIPM or CGPM or a peer-reviewed article in metrology. It is already clear to me by the fact that the official publications of the BIPM include. Also, 2 moles of hydrogen is not exactly equal to 12.044 * 10**23 hydrogen atoms, even if you were to provide more precision. Avogadro's number is an empirical determination of the number of atoms in a mole of substance. A mole is different from mere counting. Grouse 15:24, 1 September 2006 (UTC)

I am well aware of the Wikipedia policy on no original research. However, I was merely describing the means by which I found a reputable source, and thus I was no more conducting original research than someone who finds a relevant book. (I grant that there is a difference between these cases in that it is much easier to verify the contents of a book than the views of Sydney physicists, but verifiability is a different policy.)

[snip]

Ckerr 16:21, 1 September 2006 (UTC)

Upon reading more articles in Metrologia than I ever thought I would, I still haven't found any that state specifically whether the mole is dimensionless or not. The sources you cite do not explicitly address this question, as they merely confirm that the mole has units (which is not under dispute). The firmest evidence that I have found one way or another is that the mole is not included in lists of other dimensionless quantities, which indeed would tend to indicate that it is dimensioned.

I think that the best resolution is to leave the text mostly how it is, but to include a statement that the mole's dimensionality is not entirely clear. (If you think it is clear, then please find an article which states that it has dimension, as opposed to units and as opposed to it being omitted from discussions of other dimensionless quantities--I was unable to do so.) There are certainly many non-peer-reviewed sources which state that the mole is dimensionless and several arguments that it is dimensionless, and in the absence of an article that actually states it has dimension, I think it is unfair to dismiss these as simply being wrong.

Ckerr 16:50, 1 September 2006 (UTC)

OK, I did some more looking in the SI brochure, and I think this[7] pretty clearly indicates that amount of substance is one of the seven dimensions of the SI. What do you think? Grouse 18:08, 1 September 2006 (UTC)

Yes, that's unambiguous. My only criticism of the article as it stands is the use of the word "specifically" three times in one paragraph, but I think the content is now accurate and verifiable. Thanks for taking the time to find appropriate sources. Ckerr 00:10, 2 September 2006 (UTC)

Sure. Actually I think the article could use a bit of work in general... Grouse 07:29, 2 September 2006 (UTC)

From BIPM itself

I received this response from an e-mail I sent to the BIPM:

The mole is not currently regarded as a count and amount of substance is not considered as a dimensionless quantity, or quantity of dimension 1, mainly because the definition of the mole fixes the molar mass of Carbon 12 and is thus linked to the kilogram. It may be that in a few years the mole be re-defined using a fixed value of the Avogadro number. In such a case, its present link with the kilogram would relax and measuring amount of substance would reduce to a counting.

If the dimensionless mole's coffin was lacking any nails, it is certainly not now. Ckerr 12:26, 4 September 2006 (UTC)

Thanks for your diligence on this. --Grouse 13:07, 4 September 2006 (UTC)

multiples

Please don't remove multiples, for consistency they are in all seven base SI units. —Preceding unsigned comment added by 83.5.62.208 (talk • contribs)

That is not a good reason on its own. If you have a better reason please say so here. For consistency's sake I can also remove it from the other base units. Grouse 15:37, 6 September 2006 (UTC)

My reason for restoring multiples is fact of idiocy of many people for which prefix and unit creates one undividable name. For teach them truth about multiples, please restore multiples in mole. If you don't agree, please remove multiples from all seven base units. Why you are removing multiples specifically from mole, leaving them in other units? Why not better retain multiples in mole and remove them from kilogram - strange base unit with prefix? —Preceding unsigned comment added by 83.5.62.208 (talk • contribs)

I think it would be far better to teach people how to form the units with prefixes. There is already an extensive article about this at SI prefix. Adding a table to every article is just tedious and only serves to make the article longer.

Additionally, if others were to agree to use such boilerplate text, it would be far preferable to use a Wikipedia:Template. Among other things, it allows for a central place to make changes to the format of a common element to a group of pages, and to discuss the desirability of such a template. P.S. To sign a comment, just use four swung dashes like this: ~~~~ Grouse 16:04, 6 September 2006 (UTC)

Why you didn't removed multiples from metre, kelvin and kilogram? —Preceding unsigned comment added by 83.5.62.208 (talk • contribs)

I'm fine with just removing them from the ones I've removed from. You are welcome to remove from other articles if you wish. --Grouse 16:16, 6 September 2006 (UTC)

I've removed them from several of the articles - seemed a bit redundant and not needed. Prefixes should be defined and tabulated on the SI page. Next someone would want to put such a table on all the derived units as well. Vsmith 16:10, 6 September 2006 (UTC)

I made very compact template table with SI prefixes, and putted it using template link in all base units, as Grouse advised me.—Preceding unsigned comment added by 83.5.62.208 (talk • contribs)

No, I said that that is what you should do if others agreed that having this sort of information was desirable. So far no one else seems to think so. Let's just be clear on that. Grouse 17:52, 6 September 2006 (UTC)

As many Wikipedians removed prefixes from nearly all SI base units, I removed some forgotten prefix templates too from remaining base units.—Preceding unsigned comment added by 83.5.62.208 (talk • contribs)

Mole? Seriously?

The unit mol is not spelled mole, at all, ever, in the history of the world. Wow

mol is the abbreviation, but the unit is called 'mole'. --71.190.143.208 21:25, 14 October 2007 (UTC)

Could this be the entomology for mole? [8] Sithkhan (talk) 22:34, 30 September 2008 (UTC)

Rewrite

I've made some fairly significant modifications to the article, to make it more formal--and, more importantly, more accurate. There was also some minor vandalism removed. Specific points I'd like to make:

• Regarding the dimensionality of the mole, please see the preceding discussion, including the quoted passage, which was from an e-mail by Dr. Claudine Thomas of the BIPM. (While not original research, I concede that this isn't verifiable as it was personal correspondence; however, there are plenty of references to the BIPM website which say the same thing, just not as clearly as the way Dr. Thomas has stated it.) The bottom line is that the mole is not dimensionless, though it may become so if the kilogram is redefined. Hence currently the mole is not simply a unit of counting like the dozen, but it may become so in the future.

okay, Ckerr, what do you or Grouse or Dr. Claudine Thomas of the BIPM say is the dimension of quantity of stuff that is measured in moles? in terms of fundamental units what is the dimension of the unit "mole"? or of Advogado's number? what's the dimension of that? r b-j 16:12, 2 November 2006 (UTC)

In the SI[9], the dimension of mole is amount of substance. Avogadro's number has dimensions reciprocal amount of substance. Grouse 16:55, 2 November 2006 (UTC)

well, i gathered that from the NIST pages: [10] and [11], but it still begs the question. like luminous intensity which is little more than 1⁄683 watt per steradian or simply an omnidirectional source of 4 π⁄683 watt (both at 5.40 ×10¹⁴ Hz what determines luminous intensity for other frequencies is a matter of perceptual data, not physical quantity). so there is no dimensional difference between luminous intensity and power. similarly there is no dimensional difference between N_A and "dozen" or 1. it's like saying that measuring angles is not dimensionless because you have units like degrees attached to some expression. the dimension "amount of substance" is bogus and anthropometric, not fundamentally physical. the difference between mole and dozen or the difference between mole and percent (besides the hugh difference in magnitude) is that the dimensionless number represented by 1 "dozen" or 1 "percent" is exactly known and defined whereas the dimensionless number represented by 1 "mole" (that is N_A) is not known exactly under the current definition of the kilogram. not knowing the numerical value of a physical quantity precisely does not affect what dimension that physical quantity is. r b-j 17:51, 2 November 2006 (UTC)

I understand your point. Nonetheless, it is quite clear that both luminous intensity and amount of substance are currently base quantities in the official definition of the SI. Grouse 22:52, 2 November 2006 (UTC)

Of the seven "base" quantities in the SI, three are unnecessary (the mole, the candela, and the kelvin). There is discussion about how to redo the system of units in a more sensible way--please read some of the references listed on this page and on the article page. Incidentally, you're wrong that amount of substance is just like a dozen, because under the current definition the mole is an empirically determined quantity, not a constant. However, according to Dr Thomas, if the kilogram is redefined, then the mole will cease to be physically significant, and will reduce to dimensionless counting just like the dozen. Ckerr 23:36, 2 November 2006 (UTC)

i am heartened for most of what you said (that the mole, the candela, and the kelvin are essentially "unnecessary" - not sure exactly what you mean by it, but i think i agree). but a mole is like a dozen with only two differences: the first is obviously the magnitude being that N_A is much bigger than 12 and the second is that a dozen is precisely defined whereas N_A is not known exactly (being "an empirically determined quantity"). but i have to disagree with you that N_A is not a constant. it is most certainly a constant (like other physical constants or what NIST calls "fundamental" physical constants) but we just do not know, from the definition, precisely what that constant is. BTW, i had been in conversation with some NIST physicists about this myself (like Peter Mohr) and i know the issue pretty well. not everyone who works in the field agrees, even at NIST, that the Avogadro number is dimensionful. it just is not defined to a precise dimensionless number because we do not know precisely how many Carbon-12 atoms weigh exactly 12 grams. but that number, imprecise as it is, is physically dimensionless. to repeat, not knowing the numerical value of a physical quantity precisely does not affect what dimension that physical quantity is. "dimension" of a physical quantity is a different property of that physical quantity than the amount of it. if they redefine the kilogram so that N_A is a defined number, it will not change the dimension. when they redefined the meter so that c became defined to be exactly 299793458 m/s, it did not change the dimension of the speed of light from L T^-1 to something else. it is still a velocity or a speed or length per time. if N_A is dimensionless after they redefine the kg (assuming they redefine the kg in that manner, they might instead redefine the kg to fix e or $\hbar$ leaving N_A to be not exactly known) then N_A is of the same dimension (which is the dimension of 1) before such possible redefinition. r b-j 03:34, 11 November 2006 (UTC)

Actually, I completely agree with you. Personally, I think it is incredibly stupid to say that the mole has dimension, and define the units of Avogadro's number as mole^-1. For better or worse, I didn't come up with the definition, and the BIPM makes it quite clear that they think differently. I misspoke when I said that the Avogadro's constant isn't a constant; you're right, it is. What I meant to say was that it's an emprically measured constant (like the fine structure constant, for instance) rather than a defined constant (like the dozen or the permeability constant). Although I also completely agree with you that changing the definition of a quantity shouldn't change its dimensionality, apparently the folks at BIPM see it differently. Anyway, like you I spoke to some physicists and came to similar conclusions to you, and modified the article accordingly. However, it was correctly pointed out that no matter how many physicists think otherwise, they don't define the units, and if the BIPM says the mole has units, then ipso facto it has units! If you can find some reference, preferably a paper, which says that some physicists consider the mole dimensionless, please put it in. I was, to my surprise, unable to find any such reference. Minor point: by "unnecessary", I mean they can be defined in terms of other constants. Of course, this does not apply to the other four quantities, despite what some of my first-year students think (they sometimes add velocities to masses). Ckerr 09:20, 11 November 2006 (UTC)

• I disagree with the above conclusions. There are no "ipso facto" definitions, unless you are writing an article on Mole (SI). Empirically, the term mole can and has been used perfectly successfully without the stupidity of the SI's fiat definition. Many use it without knowing or without regard to that definition and many use it, as noted, with distaste for the unnecessary parts of the SI's definition. I don't mind if the article specifically lays out the SI's definition, as long as it is clear that it is the SI's definition, rather than "the" definition. It makes no sense to say that we must get the approval of measurement experts when the definition in actual use seems to differ from those you'd consider experts, especially when there are no ill effects (unknowledgeable college kids are one thing, this is another).

Perhaps the strongest argument is that the definition hamstrings the explanatory power of the article because the SI definition is conceptually flawed. I'd like to make it easy for readers to understand why a mole is used, but I can't because of "formality". Formality to get more precise descriptions of reality or to help people get better results from abstract things is one thing. Formality as an end in itself or to give allegiance in thought to a decision that many think was foolish is quite another. 12.210.82.217 08:36, 12 February 2007 (UTC)

It is Wikipedia policy that information here must be verifiable from reliable sources in the relevant field. You are welcome to provide citations to the metrological literature that support a current use of mole other than the SI one, which has also been adopted by all respected national measurements agencies. Until then, the article should reflect the SI definition of the mole.

You might also decide that the definition of the meter in terms of "distance travelled by light in absolute vacuum in 1/299,792,458 of a second" is confusing and bears little relation to how most people think about meters. But it is the only current definition that you will find supported by reliable sources. Grouse 10:53, 12 February 2007 (UTC)

• Examples that try to put the size of the mole in everyday terms have been given a separate section. I don't find the "a billion dollars a day for a trillion years" example terribly helpful, since neither a billion dollars nor a trillion years is a comprehensible concept, but I've left it in in case someone else finds it helpful. I encourage anyone to add their own examples, but check their veracity first--for example, the example about the number of human cells was dubious, so I modified it and found a reference.
• Thanks to everyone who has kept an eye out for vandalism; unfortunately it looks like we will have to continue doing so. Ckerr 11:36, 22 October 2006 (UTC)

Many thanks for this rewrite. Things are much better now. I don't really find the examples helpful personally, since as you point out, they are in terms of things that are not really that comprehensible. Grouse 13:01, 22 October 2006 (UTC)

OK, I see now - a letter from Dr. Thomas, hmm... I had removed that bit as it seemed not to be a verifiable published source. Now it's back with a link to a PDF file, OK that's better, however, scanning through the reference you supplied I see no direct support for the sentence (or maybe I'm missing something here). There is no mention of a Dr. Claudine Thomas, the supposed reference that was attached to the line I removed. Nor do I find the phrase physical significance in the PDF file. If it is your or someones else's unpublished speculating and/or interpreting the source, then it counts as original research. If the sentence However, if in the future the kilogram is redefined in terms of a specific number of carbon-12 atoms (see below), then the value of Avogadro's number will be defined rather than measured, and the mole will cease to become a unit of physical significance. is from the file then ok - but please point it out to us. PDF file Cheers, Vsmith 16:39, 30 October 2006 (UTC)

The material I was referring to was on page 77, where they propose a definition of the mole and state that "It allows the mole to be redefined in a simpler and more understandable way." There is also this article, which says "[The mole] is convenient to establish the balance in any transmutation reaction between elementary entities, but it is definitely not essential in a base units system because it is redundant with the existing macroscopic mass unit, the kilogram". That article also mentions the current physically-significant definition of the mole (footnote 8), and discusses a fixed Avogadro number alternative. Neither this article (nor the previous one I cited) explicitly states that the redefined mole would be lacking physical significance, but the purpose of an encyclopedia is to provide some synthesis of primary sources, not a collage of short snippets from them. I think the sources make it clear that the "simplification" of the mole's definition would be a result of the removal of its physical significance; if you disagree, I invite you to find a source which says otherwise! Anyway, as I mentioned on your talk page, it's usually more helpful to add a tag instead of deleting material outright, especially if you don't always check the discussion page first. If no citation is forthcoming, then delete away. Ckerr 10:47, 31 October 2006 (UTC)

Diagram

I'm not a chemist, but isn't the picture associated with this article ridiculously confusing? Wouldn't it be easier to represent whatever this image shows with text? It looks like it's saying that multiplying the moles by the mass of the constituents gives the mass. Why do we need a crazy abstract art thing to show this? Alex Dodge 06:18, 30 October 2006 (UTC)

I never really looked at the diagram before, and when I did I couldn't quite make sense of it either. It's nice to have a picture, but I think that one did more harm than good, so I've removed it. Ckerr 10:51, 31 October 2006 (UTC)

What sort of image would be helpful? Grouse 11:07, 31 October 2006 (UTC)

Perhaps a photograph of 0.012 kilograms of carbon-12? For comparison, see the metre article and the kilogram article. Alex Dodge 02:05, 3 November 2006 (UTC)

I actually already tried to look for that, but all the images I found were copywrited. If you can find one, that would be great! Ckerr 07:20, 3 November 2006 (UTC)

Definition of "dimension"

I found the ISO International vocabulary of basic and general terms in metrology ([draft third edition http://www.ntmdt.ru/download/vim.pdf]) which defines "quantity dimension, dimension of a quantity, dimension" as:

dependence of a given quantity on the base quantities of a system of quantities,
represented by the product of powers of factors corresponding to the base quantities
NOTES
1 The conventional symbolic representation of the dimension of a base quantity is a single
upper case letter in roman (upright) sans-serif type. The conventional symbolic representation
of the dimension of a derived quantity is the product of powers of the dimensions of the base
quantities according to the definition of the derived quantity.
2 Quantities having the same dimension are not necessarily quantities of the same kind.
3 In deriving the dimension of a quantity, no account is taken of any numerical factor, nor of its
scalar, vector or tensor character.
4 The dimension of a base quantity is generally referred to as ‘base dimension’, and similarly for
a ‘derived dimension’.

No mention of things being "fundamentally physical" is included. Grouse 09:15, 3 November 2006 (UTC)

Indeed. But if the kilogram is redefined, then suggestions are that the mole will cease to be a base unit, and hence the criterion for dimensionality will fail. (Similar arguments may be made for the candela and kelvin, though my guess is that the latter might be around for awhile yet.) Ckerr 15:32, 3 November 2006 (UTC)

this is correct. but i still fail to grasp why defining or knowing a quantity exactly can change its dimension. it cannot. Avogadro's number is the dimensionless number that is the number carbon-12 atoms that will weigh the same as 12/1000 of that kilogram prototype in Paris. if the mass of a carbon-12 atom is the same dimension of quantity as the mass of the kg prototype (which it most certainly is), then N_A must be dimensionless. r b-j 03:43, 11 November 2006 (UTC)

i still fail to grasp why defining or knowing a quantity exactly can change its dimension I don't see anything in the definition above about exactly knowing a quantity.

Avogadro's number is the dimensionless number No, it isn't, and I have already provided sources for this. If you wish to make a contrary assertion please provide a source in the metrological literature for it. Grouse 12:07, 2 December 2006 (UTC)

About the wording

this page needs MAJOR REWORDING none of this makes sence and is accurate. 10:17, 8 June 2007 (UTC)

Physics?

Are moles really more relevant to physics than chemistry? I've always thought of the unit as a basic unit of Chemistry. I've never used it with respect to physics, but very often for chemistry work. 71.190.143.208 21:34, 14 October 2007 (UTC)

Good point - most physicists wouldn't know a mole if it bit them. Added chemistry template, but left physics there as somebody clearly thought it was important to physics...

It is used in physics – or at least thermodynamics, that strange union between chemistry and physics. In both my Chemistry and Physics A-levels we learnt such things as pV = nRT. 212.137.63.86 (talk) 11:03, 6 August 2008 (UTC)

I got taught it in high school physics while doing gas laws. (And chemistry is just quantum mechanics by approximation anyway...) --Stlemur (talk) 11:32, 6 August 2008 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Mole (unit)/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Comment(s)

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== Physchim62 from WikiProject Chemistry == Far too much flawed science in here for me to give it a higher rating than B-Class. The mole is not a method of counting and is not like a dozen. I can count a dozen eggs, or a dozen bottles of beer, or even a dozen drummers drumming, but I can't count 6×1023 atoms of carbon-12, even if they are at rest and in their ground state! Nor can I measure the mass of an atom of carbon-12, except in relation to the mass of another atom. The Avogadro constant (not "Avogadro's number") is an experimentally measured physical constant (at least for the time being) with dimensions (amount of substance)–1. The descriptions of the calculation of molar mass are dimensionally incorrect because they were written by editors who've never heard of the molar mass constant. To talk of a mole of marshmallows is ridiculous, and only serves to confuse people into thinking that they're somehow counting out 6×1023 of something when they measure amount of substance in moles. I can only hope that editors will take a root-and-branch look at this article and improve its encyclopedic value to match its esthetic presentation. Physchim62 (talk) 23:43, 24 September 2008 (UTC)

Last edited at 23:43, 24 September 2008 (UTC). Substituted at 15:24, 1 May 2016 (UTC)

Duh?

You could read the entire article and still not understand what a mole is. Like, an encyclopedia is for people who don't know nothing to start with. Please, can we start with the definition I was taught in first year chemistry: "A mole is the atomic weight of an atom or molecule expressed in grams. Thus if the atomic weight of carbon is 12, then one mole of carbon is 12 grams. Avogadro's number is the number of atoms or molecules in a mole. Thus if carbon has atomic weight 12, one mole of carbon (12 grams) contains Avogadro's number of atoms." — Preceding unsigned comment added by 213.207.137.134 (talk) 18:49, 21 October 2015 (UTC)

winning wikipedia editors suck . they stinks at explaining any thing and that is why they do it , because they are evil anti completion commies . — Preceding unsigned comment added by 122.150.8.147 (talk) 08:52, 6 October 2018 (UTC)

• I hope this has been fixed now. --Jorge Stolfi (talk) 09:12, 21 May 2019 (UTC)

Unit?

Is a mole really a unit? In high school chemistry, I was taught that 1 mole is an amount with a value of 6.022x10^23.SamWhitey (talk) 20:31, 4 November 2008 (UTC)

Yes, it is one of the base units of the international system of units. See mole (unit). Its current definition is actually independent of the exact value of Avogadro's number (the 6.022x10^23). --Itub (talk) 15:14, 8 November 2008 (UTC)

It is a dimensionless unit.--86.125.156.119 (talk) 12:32, 31 January 2015 (UTC)

Since 2019-05-20, it is an exact pure number, like "dozen" or π.

misconception?

This entry is now moot. Since 2019-05-20, "mole" means "6.02214076×10²³ particles", exactly. --Jorge Stolfi (talk) 09:19, 21 May 2019 (UTC)

'It is a common misconception that the mole is defined in terms of [...] Avogadro's number'

...Is it? Look at the definition: 'The mole is defined as the amount of substance of a system that contains as many "elemental entities" (e.g., atoms, molecules, ions, electrons) as there are atoms in 12 g of carbon-12'.

How many atoms are there in 12 g of carbon-12? Avogadro's number!TAB (talk) 15:56, 9 July 2009 (UTC)

-I am in complete agreement. The mole can not be considered without discussing its connection with Avogadro's number. The two go hand in hand. The mole is defined in terms of Avogadro's number. —Preceding unsigned comment added by Isaac B Wagner (talk • contribs) 20:26, 18 October 2009 (UTC)

I agree. A mole of something 'is' defining the quantity numerically - it is akin to stating a dozen of something, only the implied number is bigger. Simply stating this is wrong without any justification is plainly POV pushing which I will tag as such. CrispMuncher (talk) 22:27, 12 November 2009 (UTC)

I find it strange that people are somehow unable to see this thread and accuse me of blanket tagging without providing a rationale. It it right here. It is not a full argument to be sure but I note that as yet no-one has yet made any assertion anywhere that the current article is correct. As such currently the consensus shown here is that there is a problem, because no-one has bothered to challenge this position. Indeed, the current article acknowledges the existence of sources that adopt this position but provided no countersources so casually discarding the assertion. That is fundamentally POV however you want to dress it up. The following sentence (..the mole is defined in terms of the Avogadro constant, rather than the other way around..) is IMHO a non-sequiter. The fact that the mole and Avogadro's constant are defined the way they are is immaterial to the central issue that the mole is a quantity representing a count of a number of discrete objects. Those that wish to brush this aside as purely an amount of substance would do well to explain the ambiguity in something like "a mole of oxygen". If a mole is a clear amount how can there be such ambiguity? CrispMuncher (talk) 19:35, 13 November 2009 (UTC)

The mole is not defined in terms of Avogadro's number. Look at the SI definition. Do you see Avogadro's number mentioned there? No. The key point that people miss is that you can use moles as amount of substance without having the slightest idea of the value of Avogadro's number. The reason for defining it without reference to Avogadro's number is that it allows for more precise measurements. For example, since the molar mass of fluorine is known more accurately than Avogadro's number, in principle you can measure one mole of fluorine more accurately by weighing it than by counting the atoms. I'm sure plenty of articles about this misconception have been published in the Journal of Chemical Education, but I don't have access right now. --Itub (talk) 20:47, 13 November 2009 (UTC)

So this is where the "current discussion" is. Hmm... seems Itub has provided a pretty good answer. As stated elsewhere on this page, the mole was defined and used as an amount long before Avogadro's number showed up. Chemists don't count atoms or molecules - they either go by mass (atomic weight) or molar volume for gases. As for your comparison to "dozen" (a common comparison in introductory chemistry) it's a "bit" off. A dozen is 12. A mole is equal to 6.0221415×10²³ ... but consider the uncertainty implied by that number with seven decimal places ... what about the other sixteen? That's 6.0221415×10²³ +/- 10 quintillion or so. So how is that a "count"? Bit of "ambiguity" there.

Now, if CrispMuncher cares to suggest a change in wording, we will certainly consider it. But to stuff an ugly POV tag in an article based on a misunderstanding is a bit much. I'm going to remove the tag while waiting for your suggested changes. Vsmith (talk) 00:54, 14 November 2009 (UTC)

Anyone who says the mole is a count should start by counting from from one to sixty thousand million million million… Physchim62 (talk) 08:46, 14 November 2009 (UTC)

Circular argument

Consider the measurement of one mole of silicon.

This seems a little circular — the argument that the mole is useful for measuring out a mole of silicon lacks a certain something; it certainly doesn't illustrate why it should be a unit. Similarly, if you wanted a million atoms of silicon, it would be useful to know the million, but that doesn't make "million" a unit. The only reason the mole is useful in that example is because atomic weights are expressed in conventional units that are defined coherently with the mole, rather than in yoctograms. That's a rather weak argument, especially since no reason is given why the table doesn't just list silicon atoms as weighing 46.6371yg (on average). As far as I know, the main reason is in fact convention rather than anything fundamental.

Personally, I suspect that the only real argument for the mole being a unit would be a statement to the effect that the realms of bulk matter and individual atoms are qualitatively different, such that the dimensions of one don't apply to the other.--Sabik (talk) 16:23, 5 January 2009 (UTC)

I don't think the argument is circular at all. Are you saying that the mile is only useful for measuring miles of things? Or the pound is only useful for measuring pounds of things? The point of the paragraph is to show that the measurement of amount of substance does not involve the use of the Avogadro constant. On the other hand, the measurement of the mass of atoms in yoctograms does require a knowledge of the Avogadro constant: relative atomic masses are known more accurately than masses of atoms in fractions of a kilogram: THAT is the fundamental reason why the table doesn't list the masses of silicon atoms in yoctograms. Physchim62 (talk) 22:25, 5 January 2009 (UTC)

"Are you saying that the mile is only useful for measuring miles of things?" No that's not what he's saying. It does seem pretty circular to me, too. The intro talks about the misconception of the link with Avogadro's Number and claims "[i]t is not necessary to know the number of atoms or molecules which are present in order to use the mole as a unit of measurement, and indeed the first measurements of amount of substance predate modern atomic theory and any measurements of atomic weight." Okay... so it's purportedly independent of number of atoms and the concept of an atomic weight. Later, with the silion 'example': "the convenient method is by weighing. By consulting published tables, it can easily be found that the ATOMIC WEIGHT of silicon is 28.0855.". Published tables? What a cop out. We're looking up from tables the atomic weight, but the definition is supposed to be independent of all atomic theory notions? Please. How did we find out that the atomic weight of silicon is 28.0855 without any notion of Avogadro's number or atomic theory? The mole is defined as amount of 'stuff' in 12 g of C-12. Right. Now what? How do you translate that to getting the mass of equivalent amount of 'stuff' for silicon? I could see an argument involving masses of required proportions in empirical reactions with known molecular formulae to determine the mass equivalent of 1 mole of something else given the presence of 1 mole of C-12 in the reactants. I'm not sure that would be fundamentally possible for all elements in the periodic table, and I think reaction equilibria would greatly complicate precision at best and practicability at worst. Regardless, the current silicon example is terrible and circular. Essentially it says you don't need reference to atomic weights/atomic theory/Avogrado's number to use the mole of silicon. Just look up the atomic weight in a table (gee, I wonder how that was determined). It skirts the entire problem it was trying to demonstrate the solution to, i.e. how to use the definition of a mole to determine how much is 1 mole of something else. —Preceding unsigned comment added by 64.85.36.210 (talk) 01:16, 7 January 2009 (UTC)

For ratios of reactants, you don't care about the units in the published table at all, as long as they're consistent. In that situation, you're interested in the ratio of atomic masses of your reactants, which is dimensionless. The only situation where it'd be interesting would be if someone told you the other beaker contains one mole of the other reactant, but that's no more a reason for a separate SI unit than someone telling you that the other beaker contains a pound of the other reactant, or an ancient Greek mina.

As for whether the mole is useful for anything else, I'm actually not commenting on that - I'm commenting that the example given doesn't show such other use. Sabik (talk) 18:43, 14 January 2009 (UTC)

What is the mass of one atom of carbon-12 in SI units? Explain how you arrive at your answer without using the concept of amount of substance which, in SI units, is measured in moles. Physchim62 (talk) 19:19, 14 January 2009 (UTC)

So, essentially, a mole is useful because, in SI units, amount of substance is measured in moles. Right. (FWIW, numbers, in scientific notation when necessary, can also be used to describe amount of substance. For instance, one might have 6 apples. One does not usually talk about having 10 yoctomoles of apples, even though that would be the equivalent.)

I'm not arguing here that a mole shouldn't be a unit; I'm merely observing that the example used to motivate it does no such thing, since it is circular. The solution is to replace the example with one that does actually motivate the use of the unit. Sabik (talk) 16:02, 27 January 2009 (UTC)

Well atomic weights certainly aren't determined by "weighing" atoms! Modern methods rely on Penning traps: by measuring the frequency of the radiation emitted by silicon ions and carbon ions in a Penning trap, you can tell that a silicon atom is 28/12 times heavier than a carbon atom. Older methods usually relied on measuring the change in mass of a sample when it underwent a chemical reaction. This gives a large set of ratios, which can be converted into simpler numbers by fixing the atomic weight of one element: originally hydrogen was chosen as the standard, as it is the lightest element, but oxygen proved a more practical standard (set as O = 16) as most elements form oxides. There are big problems with stoichiometry – when you first do the measurement, you can't be sure of the formula of the oxide – but there are other methods which can be used as a check, such as the Dulong–Petit law for metals or vapour densities for gases and volatile liquids.

None of these methods depend on the fact that atoms exist (well, the Penning trap sort of assumes that they do, but that is a modern innovation), much less the mass of an atom in kilograms. The first measurements of atomic weights were published by Dalton in 1808; the first estimate of the size of a molecule was made by Loschmidt in 1865; the Avogadro constant wasn't even conceived of, let alone measured, until 1909. For one hundred years, atomic weights were based on stoichiometric ratios of reactant masses: even today, the relative masses of atoms are known to some four orders of magnitude more precisely than their absolute masses (in kilograms). Physchim62 (talk) 22:21, 7 January 2009 (UTC)

Four orders of magnitude more precision does sound useful :-) Sabik (talk) 18:43, 14 January 2009 (UTC)

Speaking of circular, I would argue that "weighing" should probably be defined as determining the weight of, so how is that not what you're doing? I agree that it's sometimes more convenient to determine them in non-SI units (for instance, oxygen atom weights) but it still just amounts to weighing with a fancy scale. —Preceding unsigned comment added by 205.175.113.173 (talk) 17:51, 28 June 2009 (UTC)

The real circular argument comes if you try to define a mole as 6×10²³ atoms or molecules – how do you count them? Imagine you have a one petaflop computer which can count an atom with every floating-point operation: it would still take you 600 million seconds (200 years) to make a measurement that a high-school student can do in a few minutes!
There is a way round the circular argument – fortunately, because the mole might be redefined in this way in the future – but you have to give up the exact relation between molar mass and atomic weight. If, under the new definition, you also admit that 6.022 141 79×10²³ atoms of carbon-12 weigh approximately 12 grams (to within 50 parts per billion), things turn out OK again, at least to within the accuracy needed (and possible) in chemistry. The current measurement uncertainty in the value of the Avogadro constant would become an uncertainty in the value of the molar mass constant. But that is for the future; the current definition is as described in the article. Physchim62 (talk) 23:26, 7 January 2009 (UTC)

That's an engineering detail... essentially, it amounts to a claim that the realms of bulk matter and individual atoms are so different that it amounts to a qualitative difference. In practice, it would hardly be the first situation where the most convenient method of counting things is to weigh them in bulk. People do that with nuts and bolts. In any case, it doesn't address my complaint about the example; the example claims to show why the mole should be a unit, but it does no such thing. If you wish to replace the example with a bare statement saying that the mole is a unit because it is currently defined to be one, that would be fine, if somewhat unsatisfying. Sabik (talk) 18:43, 14 January 2009 (UTC)

It's not an engineering detail at all, it goes right to the heart of how people actually measure things. Several laboratories in the world are trying to calculate how many silicon atoms there are in sphere of silicon which weighs one kilogram: for the moment, they cannot get their result to be as accurate as other methods of measuring the Avogadro constant but they're still trying. On the other hand, the mole is used daily around the world as a measure of amount of substance without any great problems. The section states certain objections to the mole being a base unit of the SI system, which might be better treated at amount of substance except that the attacks tend to come on this article. Maybe you're not willing to admit that you can't know the mass of an atom (in everyday units) without some measure of amount of substance… Physchim62 (talk) 19:35, 14 January 2009 (UTC)

Once again, I'm mostly complaining about the example (which is circular) rather than the use of mole as a unit. Fix the example.

As for the practicalities of measurement and counting, compare with the field of astronomy — which also has many large numbers, but nobody talks about a decimole of stars (I believe that's how many there are?). While specialised units are defined, they are admitted to be specialised, for within-astronomy use only.

For the most part, though, fix the example so that it actually motivates the use of the unit… Sabik (talk) 16:02, 27 January 2009 (UTC)

According to Pieter G. van Dokkum & Charlie Conroy the number of stars in observable Universe is 0.5 mol. Neeme Vaino (talk) 04:16, 23 July 2014 (UTC)

Might as well put the 2019 answer in here. A silicon sphere, enriched in Si-28, is weighed (massed). The lattice constant (atomic spacing on some axis) and the diameter of the sphere will give you the number of atoms very accurately. Divide the mass of the sphere by the number of atoms, and you get the mass per atom. The sphere is polished very well, to be as close to a sphere as possible. Gah4 (talk) 03:12, 20 February 2019 (UTC)

Prasath Santhakumaran

Some prankster added this to the article:

"Also, it was proven that Avogrado's number was stolen off another brilliant genius in Prasath Santhakumaran. In his time of death Avogrado said that it was true that he did steal the number off Prasath and that this shouldn't be told to anyone."

This is unsourced and, as far as I know, a joke in poor taste and tantamount to vandalism on its face. I am removing it forthwith. Its author deserves some sort of reprimand. Trujaman (talk) 21:28, 7 January 2009 (UTC)

Alternate mole definitions

Apparently someone saw fit to undo the changes I made a few days ago to add a section to this article about other definitions of a mole (e.g., a kg-mol). He/she claimed that these changes were inappropriate as "These are not definitions of the mole." I must disagree: I have had numerous students confused by the use of kg-mol and lb-mol in textbooks, primarily because they too thought there was only one way to define a mole. Confusingly or otherwise, these definitions persist.

The term kg-mol is quite common among chemical engineers, and the lb-mol is even more common among chemical engineers from the USA. Software designed to assist in chemical plant design, such as PRO/II and ASPEN, all include these units. While these alternate definitions are rarely if ever seen outside the field of chemical engineering, their existence warrants at least being mentioned in an article dedicated to the definition of a mole.

Examples:

• M. S. Peters, K. Timmerhaus, and R. E. West, Plant Design and Economics for Chemical Engineers, Fifth Edition. McGraw Hill (2002-2003). [Uses kg-mol, written as such.]
• J. M. Douglas, Conceptual Design of Chemical Processes. Boston: McGraw Hill (1988). [Uses lb-mol, written as mol, throughout.]

Kaiserkarl13 (talk) 21:46, 20 January 2009 (UTC)

The pound-mole (also written without the hyphen) is a separate unit, although the link currently redirects here. The "kilogram-mole" is just an obsolescent name for the kilomole. Both of them are units of measurement of amount of substance that can be found in some US texts, but neither of them is the same unit as the mole. The confusion only arises if you pretend that they are. Physchim62 (talk) 22:12, 20 January 2009 (UTC)

The fact that pound-moles and kilogram-moles are separate units but are still called moles was my point! The fact that kilomoles and kilogram-moles are the same is a result of the fact that kilo(grams) and (kilograms) are the same, but the kg-mol is in no way an obsolete unit---it just happens to have the same meaning as a kmol and takes more characters to type. The purpose of the added text is to point out that there is more than one definition of a mole---with the standard SI unit of a mole being defined in terms of the gram. There's nothing pretend about it, though---the units kg-mol and lb-mol still occur, and they are no less valid as definitions of a mole. They just aren't the ones associated with the SI definition of "the mole." Kaiserkarl13 (talk) 23:00, 20 January 2009 (UTC)

You'd never say that pounds are another way of defining grams, so why do you say that the pound-mole is another way of defining the mole? It's another way of defining a unit of amount of substance, yes, but there is no law that says that all units of amount of substance have to be called "moles": in fact, there is a good pedagogical case for pointing out the exact opposite! Physchim62 (talk) 23:14, 20 January 2009 (UTC)

I'm not contending that the specific unit referred to as the mole (i.e., the SI unit defined as the number of entities in 12 g of 12-C) is the same unit as a kilogram-mole---obviously it isn't. The point of contention is that other units of amount of substance are invariably also called moles (with some modifier), perhaps merely due to lack of creativity. An excellent example is the unfortunate use of pounds in the English Imperial System to refer to both units of force and mass (these are, of course, different but related units). I think this point of contention could be settled by adding a section titled something like, "Units related to the mole" in which other units of amount of substance are defined. This would have the advantage of clarifying that "the mole" (unit) and "a mole" (generic term for amount of substance, usually but not always referring to the SI unit) can be different things. This would also solve the problem of pound-mole and kilogram-mole currently redirecting to Mole_(unit), which doesn't mention either of these other units. I may write these articles at a later date when I have the time. Kaiserkarl13 (talk) 21:35, 21 January 2009 (UTC)

Possibly this should be "Other units called mole" or something on those lines? That would make it clear that the lb-mole and kg-mole (both of which redirect here) are not actually the mole but rather something else with a confusingly similar name… I think I'll go add that. —Preceding unsigned comment added by Sabik (talk • contribs) 16:15, 27 January 2009 (UTC)

I have re-written the section, trying to be brief and non-contentious, while giving a source and giving the style of an encylopedia. I hope this helps. Chemical Engineer (talk) 17:52, 5 February 2009 (UTC)

Chronologically?

"(also, anachronistically, known as "Avogadro's number")" Wha-Huh? "Anachonistically", chronologically out of order? Does that mean that yesterday it was correct, but today it is not correct? Maybe it means that it will be correct in 1.66 years. I'm not asking if it is correct to call Avogadro's constant, Avogadro's number. I'm asking what time has to do with it. —Preceding unsigned comment added by 207.5.226.78 (talk) 12:16, 7 April 2009 (UTC)

When it was first measured, it was assumend to be a pure number because people didn't stop to think that its value depends on the units used to measure amount of substance. Now it is generally accepted that amount of substance is a separate dimension in any practical system of macroscopic units of measurement, and so it is proper to call it the Avogadro constant to recognise the fact that it is not a pure number, but a physical constant with a unit (mol^–1). Physchim62 (talk) 13:25, 7 April 2009 (UTC)

But now it is 2019, and Avogadro's constant will (soon) be defined as an integer number per mole, and so Avogadro's number an integer. They could have defined it as rational non-integer, an irrational number, or even a transcendental number. Gah4 (talk) 03:21, 20 February 2019 (UTC)

Etymology

This article says:

The name is assumed to be derived from the word Molekül (molecule). The first usage in English dates from 1897, in a work translated from German.

That seems at best incomplete. The Oxford English Dictionary says

[< French molécule (1674) < post-classical Latin molecula (P. Gassendi Syntagmatis Philosophici (a1655) II. §1. III. vi, in Opera Omnia (1658) I. 271/1) < classical Latin m{omac}l{emac}s mass (see MOLE n.2) + -cula -CULE suffix.

and then of the -CULE suffix says:

suffix, corresp. to F. -cule, ad. L. -culus, -cula, -culum, dim. suffix of all three genders: see -CULUS. In living words, the suffix underwent various phonetic changes in becoming French; e.g. articulus, orteil; auricula, oreille; cuniculus, conil; masculus, masle, mâle; but it remained as -cle after persisting consonants, as in avunculus, oncle; cooperculum, couvercle. After the latter, some words of learned origin were fashioned in -cle; e.g. article; but in modern times the L. ending has been usually adapted in F. as -cule, as corcule, cornicule, corpuscule. In English, both endings -cle and -cule are found, as corpuscle, corpuscule, crepuscle, crepuscule, animalcule, formerly also animalcle, floscule, versicle, etc. The L. endings -culus, -culum are sometimes retained unchanged: see -CULUS. The ending -cule, with connecting vowel i, is sometimes employed, after L. analogies, to form contemptuous diminutives, as poeticule: cf. criticule.

The term "dim. suffix" means "diminutive suffix", so things bearing that suffix are small. So "mole" means "mass" and "-cule" makes it diminutive, so "molecule" is a small mass.

Thus "mole" did not come from "molecule", but rather "molecule" came from "mole" by the addition of a suffix. Michael Hardy (talk) 19:49, 7 April 2009 (UTC)

PS: "Assumed" is very vague! Assumed by whom??? Some anonymous Wikipedia editor, maybe?? Michael Hardy (talk) 19:50, 7 April 2009 (UTC)

The word "mole" certainly doesn't come directly from the Latin mole! You might like to read some of the references in the article before engaging in such vain speculation. Physchim62 (talk) 18:36, 28 June 2009 (UTC)

Michael Hardy: you seem to be quoting from the OED entry for molecule, n., not that for mole, n.⁸, which is why you have reached the wrong conclusion. The OED tells us that mole (English; the unit) comes from Mol (German), which comes from Molekul (German) (although that last step is not explicitly stated in the Ostwald 1893 book). There's no point in tracking it back any further, since the origin of Molekul is obviously, like that of molecule, ultimately from Latin.

I do agree with your postscript, that "assumed" is vague. The assumption seems to have been made by the OED, so we should say that. --Heron (talk) 18:18, 30 January 2010 (UTC)

National Mole Day

The radio advised me this morning that today is National Mole Day. Who’d have thought?

The mole is a wondrous thing, and easy to understand – as long as you realize it is just a number:

• If you have a dozen eggs, you have 12 eggs.
• If you have a baker’s dozen of buns, you have 13 buns.
• If you live a score of years, you live 20 years.
• If you have a Groß (or gross) of hobbits you have a dozen-dozen, or 144 hobbits.
• If you have a ream of paper, you have 500 sheets or paper
• If you have a bale of paper you have 5000 sheets of paper
• If you have a Maß (or ‘great gross’) of tacks, you have a gross-gross (a dozen-dozen-dozen-dozen) or 1728 tacks.
• If you have a Mole of atoms, you have 6.02 X 10²³ atoms
• If you have a nonillion freckles, you have 10³⁰ (or perhaps 10⁵⁴, depending upon where you live) freckles
• If you have googol of edits, you have 10¹⁰⁰ edits.

What could be simpler?

But to the question: Is "National Mole Day" encyclopedic enough to be included in a Wikipedia article?

Skål - 130.20.3.152 (talk) 16:37, 23 October 2009 (UTC)

Of course, we even have an article about it: Mole Day. --Itub (talk) 14:57, 26 October 2009 (UTC)

POV Section

"The mole as a unit" is POV (and has a disputable match between content and heading):

The most blatant is the phrasing "The second misconception" referring to something which could be taken both as true and as a matter of perspective. This is the worse as the author borders on straw-manning by equating the originally stated criticism "the mole is simply a shorthand way of referring to a large number" with "that the mole is simply a counting aid", formulations that are not equivalent (albeit related). Notably, the "second" also implies that the previously discussed item is a misconception---which is equally disputable.

Looking more in detail on:

Claim 1: I must second that the mole is dimensionless and it lacks the significance of e.g. the meter. (Notwithstanding that it may be justified as a unit.) It is better compared to % (per cent): Handy and useful, but not truly significant. Further, it is redundant when the mass and composition is known. The argumentation against this is partially specious. The number of particles of the involved elements can easily be computed when mass and composition are known (and, conversely, knowing the number of particles and composition, the mass is easy to find). Without knowing the composition, OTOH, the concept of moles would typically be useless. In effect, moles and the associated calculations are a handy help, but are still redundant. That the number of moles can be found without knowledge of mass is irrelevant, because the number of moles and mass can always be found from each other when composition is known.

(There are some special cases where the equivalency fails, e.g. in relativistic conditions; however, the calculations can be adapted and mathematical equivalency of information is preserved. Further, while the ideal gas law may give some physical characteristics based on number of particles alone, these are of limited value, and more advanced models use characteristics other than particles alone, which require that composition, or other characteristics which lead to mass or possibly a mass surrogate, is known.)

Claim 2: Whether the mole is defined in terms of Avogadro's constant, or the other way around, is irrelevant. It is a short-hand for a large and arbitrary number. The other gains from using moles could be found by using the atomic weight directly. (With the exception of some handy approximative jumps from weight to number of moles when doing head calculations.)

In short: Apart from convenience, the mole has no advantage over the number of particles (as a "vanilla" number, just like 10 % has no advantage over 0.1). Apart from convenience, very little is gained from using moles instead of mass. Michael Eriksson (talk) 13:29, 23 January 2010 (UTC)

Agree that, while there may be some interesting points, it is presented in the form of an argument, not encyclopedic. Noloop (talk) 21:00, 9 April 2010 (UTC)

6.0221415 × 10²³ / 0.012?

The kilogram is the mass of exactly (6.0221415×10²³⁄0.012) unbound carbon-12 atoms at rest and in their ground state.

This seems a strange way to write it. Is it really planned that the official definition will be written like this, rather than simply as 5.01845125 × 10²⁵? Any idea why? — Smjg (talk) 23:06, 17 May 2011 (UTC)

If you follow up the links in New SI definitions, you can see the full story. Martinvl (talk) 06:17, 18 May 2011 (UTC)

~1.660539 ymol of quark conversions were used to produce a proton. see W_boson#Weak_nuclear_force — Preceding unsigned comment added by 193.199.19.150 (talk) 06:43, 29 March 2012 (UTC)

Is it accidental that Avogadro's number is divisible by three? Gah4 (talk) 19:26, 20 May 2019 (UTC)

It seems that it isn't. I was looking at the number above, but it is actually 6.02214076×10²³ reciprocal mole (mol⁻¹), so not a multiple of three (or 12). Gah4 (talk) 19:33, 20 May 2019 (UTC)

Redefinition

Definitions: Section 4 and 4.1 considering a new definition of the kilogram does not belong in this article on the mole, amount of substance - the section should be removed or rather moved to the kilogram page. On the other hand it is proper to consider redefining the kilomole (kmol) as a basic SI unit rather than the mole. I see no difficulty in doing this and retaining all the definitions of Avogadro's number (and others) as they are at present. What it will do is make the basic SI definitions a coherent* set rather than include the odd man out, the mole.

• I note that Wikipedia doesn't contain this notion in its list of coherence definitions - I will endeavour to elucidate soon.

Scanrod (talk) 11:23, 19 June 2010 (UTC)

In what sense is the mole the "odd man out" at the minute? Physchim62 (talk) 11:40, 19 June 2010 (UTC)

I have hidden this.

A decision on this proposal is expected by the CGPM in October 2011.

It cannot be true since October 2011 is now past. So was a decision made? If so, what was the outcome? If not, what are they saying now? JIMp _talk·cont 01:08, 8 December 2011 (UTC)

I posted a link to the CGPM 2011: see resolution 1. I think we can now delete the section about the kilogram from the mole article. --Hroðulf (or Hrothulf) (Talk) 17:05, 12 December 2011 (UTC)

Kilogram section now removed per Scanrod's request. --Hroðulf (or Hrothulf) (Talk) 17:10, 12 December 2011 (UTC)

Consistency between articles

In various articles around Wikipedia that make use of Avogadro Number (such as Avogadro's Number and this article, and many of the articles that use Avogadro's Number in calculations), the actual number used differs. And even more unfortunately, most of these articles have cites that "prove" their number correct. Is there any way we can enforce consistent use of the number, or make reference to one "superior" cite that provides the most up-to-date and accurate number? --Nick2253 (talk) 03:38, 6 November 2012 (UTC)

Examples please? Martinvl (talk) 04:35, 6 November 2012 (UTC)

A citation only proves that someone (which is being cited) made some statement, not the statement itself. In this case, there have been quite a few experimental measurements of the Avogrado's Number over the years. One needs to look at the year of the citation to see which is more recent. I agree that it would be good to have a tool that automatically updated the value (and the information source) in every page it appears.

177.138.210.163 (talk) 02:00, 25 March 2017 (UTC)

Confusion

Is there sometimes the mole confused with the molar mass in some sources by abuse of language?--86.125.160.200 (talk) 15:59, 10 January 2015 (UTC)

Kindly see typo mistake in first part "For example, the chemical equation 2 H2 + O2 → 2 H2O implies that 2 mol of dihydrogen (H2) and 1 mol of dioxygen (O2) react to form 2 mol of water (H2O)." It should be 2H2+ 0 and not O2. M S DIVEKAR (talk) 17:58, 5 September 2015 (UTC)

The equation is balanced as written. Vsmith (talk) 18:34, 5 September 2015 (UTC)

Deletion of molar mass - atomic mass ratio demonstration

This entry became largely moot after the redefinition of 2019-05-20. For practical purposes, one does not need such detail. For "talmudic" accuracy, the amu is now an experimental measurement while a mole is an exact number of particles. --Jorge Stolfi (talk) 09:28, 21 May 2019 (UTC)

I found these sentences, and I only reformatted them:

We can derive the relationship between a mole of a substance and the mass of one atom/molecule of the substance using the definition of the mole stated above and the relationship between a gram and an amu (there are Avogadro's-number of amu in a gram of a pure substance) like so:

Mass of 1 hydrogen atom = 1.008 amu.

Mass of 1 mole of hydrogen = 1.008 ⋅ [6.022 141 29(27) ⋅ 1023] amu = 1.008 g.

Mass of 1 hydrogen atom = 1.008/6.022 141 29(27) ⋅ 1023 g.

We now compare the mass in grams of 1 hydrogen atom with the mass in grams of 1 mole of hydrogen. By dividing the mass of 1 mole of hydrogen by the mass of 1 hydrogen atom we'll obtain the scale-factor between the mass of 1 hydrogen atom and the mass of 1 mole of hydrogen (we will use the numbers that are 2 lines above this one). Since dividing by a fraction is the same as multiplying by that fraction's reciprocal, we can see that the scale-factor is:

mass of 1 mole/mass of 1 atom = 1.008 g ⋅ 6.022 141 29(27) ⋅ 1023/1.008 g = 6.022 141 29(27) ⋅ 1023 = NA 

This scale-factor holds true for all pure substances. For example, a mole of water is Avogadro's-number times the mass of one water molecule (H2O).

But I think it is a not very useful demonstration, that overload the page and make it difficult to read. I suggest to remove it. --Fornaeffe (talk) 11:29, 7 February 2016 (UTC)

name acquire

two basic units are named after scientists; A[mpere] and Ke[lvin], so what if this ambiguous name labeled after Jons Jacob the Be[rzel]. and mmol and Kmol can be mBe and KBe. and a katal would be Be/sec
Tabascofernandez (talk) 00:19, 15 July 2017 (UTC)

• Well, this is not the forum to discuss such proposals. Wikipedia only describes standards, it does not make them. --Jorge Stolfi (talk) 09:25, 21 May 2019 (UTC)

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Mass versus weight

Recent edits have a Mass versus weight problem, specifically in that there is no verb for measuring mass corresponging to to weigh. Even though in popular usage, this distinction is ignored, it shouldn't be ignored here. Gah4 (talk) 21:04, 2 February 2019 (UTC)

I contend that to claim "there is no verb for measuring mass" is false: just because we have specialized the noun weight to exclude the meaning mass does not imply that the verb weigh has become inappropriate for determine the mass of. What was in the article before my edit, namely the use of the verb "is" (used to mean "has a mass of"), was far, far worse (the linguistic equivalent of "a cat is 2 kg"). However, there are easy, albeit more long-winded workarounds – see what you think of my next edit. —Quondum 21:36, 2 February 2019 (UTC)

The question was already in Talk:Mass versus weight, but I agree that "weigh" is better than "is", but could we do even better? I will watch for more edits. Gah4 (talk) 21:40, 2 February 2019 (UTC)

The MoS seems to generally recommend rewording issues like this in a way that allows the issue to be avoided entirely (be it ambiguity, region-specific language or the like). My rewording "... weighs ..." to "the mass of ... is ..." is this; it turned out to be less clumsy than I had anticipated. —Quondum 22:16, 2 February 2019 (UTC)

For info, I happened across this text in the IEEE SI 10-2016 'American National Standard for Metric Practice' §C.6.2:

"The weight of a body in a particular reference frame is defined as the force that the body an acceleration equal to the local accelaration of free fall in that reference frame."

"The verb to weigh means 'to determine the mass of' or 'to have a mass of'."

—Quondum 22:55, 2 February 2019 (UTC)

US units make it confusing, no matter what you do. One of my favorite is specific impulse which for a rocket (or jet) is the thrust divided by the weight (not mass) per second of fuel used to generate it. (For a jet engine, the air is not counted.) The result is a unit of seconds, the same in either metric or US units. But also, in a nearby air museum, there is a display on characteristics of jet engines with thrust in pounds and kg. It seems that there is an official (like our MoS) document for museums that says newtons, so they will redo it. Also, propeller plane engines are rated in HP and kW. Thanks for the fix. Gah4 (talk) 03:26, 3 February 2019 (UTC)

6.022 listed at Redirects for discussion

An editor has asked for a discussion to address the redirect 6.022. Please participate in the redirect discussion if you wish to do so. _signed, Rosguill ^talk 22:05, 11 May 2019 (UTC)

change

I presume this will eventually be updated to the new definition, but it seems to me that, for just about all ordinary chemistry, it doesn't change anything. One still gets out the periodic table, adds up the atomic mass of all the constituents, and measures out (avoiding the word weigh) the appropriate amount. Common laboratory balances aren't precise enough to make a difference. Seems to me that, now that there is a difference, the article should explain it. Gah4 (talk) 19:21, 20 May 2019 (UTC)

• Done. Indeed it does not change anything for practical purposes. The change is of interest only to very demanding metrologists and historians. --Jorge Stolfi (talk) 09:23, 21 May 2019 (UTC)

The change is of interest for huge amount of students which learns the concept in college/Gymnasium etc. But correct, it do not have practical consequences. Christian75 (talk) 16:15, 21 May 2019 (UTC)

elemental formula

There is in this article a link to elemental formula. I didn't follow the history, but either the link, or the redirect, is wrong. I believe that either or both formula mass and formula weight are more appropriate for the discussion here, though neither are discussed in the article. As noted, formula mass/weight makes sense when the actual unit isn't a molecule. I suppose ionic solids in gas form might form such molecules, but that normally isn't important. For polymers, the actual molecules are much larger, and formula mass/weight makes more sense when discussing them. That is especially true for copolymers, where the molecules used to generate them are different. Gah4 (talk) 16:29, 21 May 2019 (UTC)

Any more thoughts on this? There is no good discussion, as far as I know, for formula mass and formula weight, specifically for things like ionic crystals. The redirects aren't so good as they could be. Gah4 (talk) 18:08, 21 June 2019 (UTC)

When should moles be used?

Since I can technically use grams in the same measurement where I could use moles (like in blood tests some labs use grams some moles). Is their a guide as to when to use which? Jake9wi (talk) 21:41, 7 March 2020 (UTC)

Relevance

Avagadro's Constant(The number of atoms/molecules in a mole) should be listed on this page for ease of refrence. As I just did. Also, since it's impossible to count the number of atoms/molecules in something with anything representing a reasonable accuracy, I was rather confused when someone claimed that a mole (The number of atoms so that an object weighs it's atomic weight in grams) is not based off of how many atoms there is?

Anyway, you need to know how many atoms there are if you're trying to do Thermo Dynamics equations and need to convert from molecules to moles so you can apply the Ideal Gas Law. 63.228.160.115 (talk) —Preceding undated comment added 19:57, 30 August 2009 (UTC).

• With the new definition of mole, Avogadro's number now is an exact constant.--Jorge Stolfi (talk) 09:15, 21 May 2019 (UTC)

Might note that the redefinition that they didn't use involves a silicon sphere measured to amazing accuracy. Since the lattice constant is known to many digits, and the sphere radius can be very accurately measured, the number of atoms is also very accurately measured. But they didn't use that one, anyway. Gah4 (talk) 18:44, 25 November 2020 (UTC)

NPOV and self-citations

A new reference was added to the lede. Reference [1] is the SI-definition of mole, and reference [2] is a 2020 paper by Klaus Schmidt-Rohr, added by editor Klaus Schmidt-Rohr. This might be an instance of self-promotion, and might go against the NPOV pillar of Wikipedia.--Theislikerice (talk) 14:23, 25 November 2020 (UTC)

For now, I think it can stay. A quick look shows that he has enough papers, that he doesn't need a lot of self promotion. Though having a lot of papers could be a sign of the need for self promotion, it also shows a lot of work. Does the reference seem to make sense? Gah4 (talk) 18:41, 25 November 2020 (UTC)

Mole concept

Mole is considered as seventh basic S.I unit of the amount of the substance. In Latin the word 'mole 'means heap or pile 160.238.74.104 (talk) 05:31, 20 March 2022 (UTC)

Incorrect changes

Fgnievinski, I don't want to get into and edit war, but I am going have to revert your last change again. You have introduced too many errors predicated on your premise of dimensionlessness of amount of substance, for example, The mole (symbol mol) is a unit of measurement defined as exactly 6.02214076×10²³ elementary entities. implies this, and ... the Avogadro number, having the same numerical value as one mole makes no sense whatsoever. I am not going to pick through your changes and fix the errors: it is not my function to tutor you on your misunderstandings. Please properly understand content that you choose to change before you change it. If you have an issue with this, please take it up at WT:PHYS, since this issue extends beyond this article. —Quondum 16:58, 10 July 2023 (UTC)

So what's the meaning of "unit" in "mol (unit)" if not a unit of measurement? I've posted a notice at Wikipedia_talk:WikiProject_Physics#Mole_(again) about the discussion here. And here I quote the SI brochure (9th ed.) [12]:

The mole, symbol mol, is the SI unit of amount of substance. One mole contains exactly 6.022 140 76 × 10^23 elementary entities. This number is the fixed numerical value of the Avogadro constant, N_A, when expressed in the unit mol^−1 and is called the Avogadro number.

Hence the Avogadro number has the same numerical value as one mole: 6.022 140 76 × 10^23; for the distinction between numerical value and units, see Dimensional_analysis#Incorporating units. Are you implying the SI is wrong? fgnievinski (talk) 17:02, 10 July 2023 (UTC)

Ok I think I understand @Quondum's objection. The phrase "same numerical value as one mole" is not something I can figure out. My brain says "erm, ah, one? is 'one' the numerical value of one mole?" Similarly "the Avogadro number has the same numerical value" challenges me because the Avogadro number is a number: it doesn't need or want the consideration "numerical value".

To me, the two sentence quote from SI would be a great addition to the article, in place of the current sentence relating the mole, number, and constant.

HTH, Johnjbarton (talk) 01:03, 11 July 2023 (UTC)

I'm having a hard time sorting out what is the issue here. The revert linked under "your last change" has a comment "(rm excess linking)" so it does not seem to be related to the questions here.

The current article says:

• Closely related quantities are the Avogadro number, having the same numerical value as one mole;

To me it seems that this sentence would be more clearly written:

• The number of entities in a mole equals the dimensionless Avogadro number;

But I don't know if this is related to the discussion or not. Johnjbarton (talk) 17:34, 10 July 2023 (UTC)

This appears to be a perennial language issue. The number of marbles that fit into a volume of one litre might be 1000; this does not justify equating one litre to 1000 entities. The fact that fgnievinski does not realize, combined with persistent invalid updates based on this kind of misunderstanding is intensely frustrating. The logic "Hence the Avogadro number has the same numerical value as one mole: 6.022 140 76 × 10^23" is just as semantically nonsensical. The Avogadro constant is a dimensional constant. It never makes sense to say that some dimensional constant "has a numerical value of ...". We can refer to the numerical part of a dimensional quantity when the unit is specified, but that is equivalent to dividing the dimensional quantity by another, namely the given dimensional unit.

The SI is not wrong; you are just interpreting it completely incorrectly. To elaborate on what Johnjbarton says, it would be more correct to say "the number of entities contained in one mole of substance is ...". Notice that this is the word that the SI uses. It is not a matter of being "clearer", it is a matter of correcting an outright error. Just as I would say that the mass of water contained in 0.001 m³ of water is 1 kg. This would not fool anyone into saying that one litre has the same numerical value as one kilogram, or any statement similar to what you are saying. —Quondum 00:26, 11 July 2023 (UTC)

A quick glance at section Criticism readily reveals controversy published in the peer reviewed literature about the nature and interpretation of the mole. It's not with harsh and dismissive language that someone will be able to pretend there's no debate around the concept. One can reasonably and consistently interpret: a mole to be defined as exactly equal to the Avogadro number: mol=N0; the amount of substance, in moles, as multiples of the Avogadro number: n=N/NA=(N/N0)mol, or n/mol=N/N0; the Avogadro number just as a historical named large number; and the Avogadro constant as the Avogadro number divided by one mol: NA=N0/mol. One mole "contains" N0 entities no more than the number 100 contains one hundred integers - there's no need to claim anything esoteric around the concept. "One mole of stars" is a common idiom meaning simply a set of stars in quantity equal N0. fgnievinski (talk) 02:30, 11 July 2023 (UTC)

The mole, being a creation of SI for the purposes of this article, should be described consistent with the SI don't you think? In your previous comments you cited SI as an authority; it seems we should rely on it for the definition as well as report criticism of their decisions. But altering their definition does not seem proper.

You say: "One can reasonably and consistently interpret: a mole to be defined as exactly equal to the Avogadro number". To me this is puzzling. A mole is unit, not a number. It cannot be exactly equal to a number. But my puzzlement and opinion are not more valid than yours. On the other hand, SI's stated definition is more valid and they do not define a mole in this way.

If you have some references to additional criticism along the lines of your concerns we should include these in the Criticism section. Johnjbarton (talk) 03:26, 11 July 2023 (UTC)

The situation is not unlike in the radian, a dimensionless unit also equal to a pure number (in that case simply 1). It's all well explained in the article Amount of substance and the mole in the SI:

"The amount of substance 1 mol always contains the same number of specified entities. This number is identical to the Avogadro number, the numerical value of the Avogadro constant." (...) "The new definition relates the mole to a fixed number of elementary entities, explicitly based on a fixed numerical value of the Avogadro constant" (...) "The mole will also be clearly linked to a count, in such a way that the Avogadro constant acts as the constant of proportionality linking counting of elementary entities with amount of substance."

I'm afraid older folks might be too hang up on the older definitions of the mole, which is now mostly left for the realization and measurement traceability of derived measurements:

"the definition of the mole is no longer tied to the definition of the kilogram, although for the foreseeable future the vast majority of practical realizations of the mole and its derived units will still involve weighing via n=m/M where n is the amount of substance, m is the mass of a pure sample and M is the molar mass (mass per amount of substance)." (...) "The new definition of the mole will remove any link between mass and amount of substance: the mole will not rely on any other units or defining constants for its definition."

fgnievinski (talk) 04:59, 11 July 2023 (UTC)

The situation with radian and mole would be exactly analogous if mole was defined as a derived unit (which I would find more logical). But it is defined as a base unit, and that makes it different. Within SI, the equation $N_{0}=1\,{\rm {mol}}$ is dimensionally incorrect. In contrast, $1\,{\rm {rad}}=1$ is dimensionally correct. It is of course possible to define a natural system of units where $N_{0}=1\,{\rm {mol}}$ and $N_{A}=1$, but then it is not SI anymore. Jähmefyysikko (talk) 07:05, 11 July 2023 (UTC)

Thanks, but I don't see how any of this is relevant to the issue being discussed here. (To be honest I'm yet to see any specific proposed text for the article that differs from what we have other than my proposal to insert the SI definition verbatim.)

The only issue I can sort out is from your comments where you want a mole to be a number, but that is clearly not what SI says it is. The passage you just quoted is clear:

"The amount of substance 1 mol always contains the same number of specified entities. This number is identical to the Avogadro number,..."

Thus when you count the objects in a mole you get a number; the mole is a set, not the cardinality of the set. Johnjbarton (talk) 15:04, 11 July 2023 (UTC)

Oh well, NA=1 could still be interpreted consistently with the SI usage, NA=N0/mol. That way, the amount of substance, n=N/NA=(N/N0)/mol=N, could be expressed in the usual "moles" (multiples of the Avogadro number) or directly as a particle count (multiples of 1). Despite the numerical difference, the two expressions would be equivalent, like any quantity equation (e.g., 1ft=0.3048m).

This is not an uncommon view; it has been implemented in software such as UCUM, whose documentation states [13]:

"the mole is essentially a count of particles expressed in a unit of very high magnitude (Avogadro's number)" (...) "The Unified Code for Units of Measure defines the mole to be the dimensionless Avogadro number" (...) "The Unified Code for Units of Measure identifies the mole with the Avogadro number"

But, alas, the SI decided to make the mol a base unit (thus irreducible) and to give special status to "amount of substance" (always in moles), distinguishing it from the ordinary number of particles (in arbitrary units: unit multiples, dozens, etc.). The SI brochure only goes so dar as stating: "The amount of substance, symbol n, of a system is a measure of the number of specified elementary entities." Hopefully in the future they'll demote the mole and treat it on an equal footing with all other counting quantities.

Meanwhile, I've re-edited the text to make it more aligned with the SI wording and your feedback here. Unfortunately, it's hard to avoid almost a circular definition involving all concepts: N, N0, n, mol. fgnievinski (talk) 03:15, 12 July 2023 (UTC)

Thanks for the changes. IMO, in SI the situation with the electromagnetic (ampere) and luminous (candela) dimensions is not that different from that of the mole. Both can be expressed in terms of mechanical dimensions, but one gets more practically sized units by introducing an extra dimensions. So instead of considering the 'baseness' of the mole as a defect in SI, it can also be viewed as a practical design choice. Jähmefyysikko (talk) 08:56, 12 July 2023 (UTC)

It is good to view this as a "design choice". The extra "physical dimensions" are an artefact of definition (and hence calling them "physical" is a misnomer), but nonetheless are very effective and useful. But unlike amount of substance and temperature, the scale of normalization for electromagnetism is not as natural as you seem to think. For example, the Gaussian system made an unfortunate choice of normalization, leading to some unnatural formulae. Also, following the same normalization procedure, mass would inherently be "expressed in geometric dimensions", but I don't see anyone arguing for that. If you were to allow the rationale of "can be expressed in terms of mechanical dimensions" to its extreme, you end up with any of numerous incompatible "natural" systems. Keeping the additional dimensions avoids all this arbitrariness and is compatible across disciplines, avoids confusing the layman, and is a clean albeit non-minimal system. Angle is an example of something that would benefit us immensely if similarly defined as an independent dimension. One could argue for demoting temperature to being on an equal footing as energy per count, since the same argument applies as for demoting amount of substance to a counting quantity. However, that would lead to endless confusion and practical inconvenience, just as treating amount of substance as a count would, and indeed angle as a dimensionless number does. —Quondum 11:05, 12 July 2023 (UTC)

I agree, there is no natural normalization for EM, the variety of CGS units demonstrates that well enough. And geometrized mass is probably only used by some theorists to simplify the equations. For practical measurements it would be be a step into the wrong direction. Jähmefyysikko (talk) 19:05, 13 July 2023 (UTC)

In the midst of this long discussion on semantics, I think a key point has been missed: the lead is moderately incomprehensible IMHO. I suggest a KISS rewrite that is understandable to a 15 year old, or an adult who never liked science. I am currently buried, but as someone outside (to date) this discussion I could do this in some days. Ldm1954 (talk) 11:50, 18 July 2023 (UTC)

Please be specific about what you find incomprehensible (or think would be incomprehensible to that target audience). I don't think my 15-year-old self would have had any more trouble understanding this lead than I would an Encyclopaedia Britannica article (which keeps a far lower standard than Wikipedia does, IMO). That is also not the primary target audience for our science articles, even the leads of our science articles. Think more "interested late-senior-schooler". —Quondum 13:21, 18 July 2023 (UTC)

I have noted, maybe not here, about the SI meaning of base and derived units. Note for example that the meter is defined in terms of the second and the speed of light, so should be a derived unit, but isn't. There are others that also have this problem. So I am not at all surprised that they get mole wrong. Gah4 (talk) 19:25, 18 July 2023 (UTC)

Other units that also have the "problem" that their status as base or derived units does not follow the dependencies of the associated definitions? It is not a problem; it is a given. Such a suggestion is also out of scope: this is not what talk pages are for. —Quondum 00:47, 19 July 2023 (UTC)