Talk:Chemical element

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I've always thought that a chemical element is a... er... totality of atoms with the same number of protons/same atomic number, but not a chemical substance. It seemed to me that elementery substance is the right term for a substance consisiting of atoms of the same chemical element only. Anyway, the definition is a mess: "A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons."--Adnyre (talk) 11:05, 9 January 2010 (UTC)

Consider this: chemical element
1. A species of atoms; all atoms with the same number of protons in the atomic nucleus.
2. A pure chemical substance composed of atoms with the same number of protons in the atomic nucleus. Sometimes this concept is called the elementary substance as distinct from the chemical element as defined under 1, but mostly the term chemical element is used for both concepts.
IUPAC Compendium of Chemical Terminology 2nd Edition (1997)
We should rewrite the definition.--Adnyre (talk) 11:31, 9 January 2010 (UTC)

Chemically pure and isotopically pure[edit]

OK, the above problem in the intro was apparently resolved by deleting the repetitious second sentence. But today a second conflicting definition was added to the Allotropy section, stating that a pure element is one that consists of only one stable isotope. This is also referred to a reliable source, namely the European Nuclear Society website. However it conflicts with the definition in the intro - for example, carbon is a pure element according to the first definition (since all its atoms have 6 protons) but NOT according to the second (since it has two stable isotopes, C-12 and C-13). A quick Google search suggests that both definitions have many adherents.

So what should this article say? Since there seem to be two widely accepted definitions, we should present them both and make the distinction clear. I suggest we first present the older definition (same element, same number of protons) which is described as chemically pure when the distinction is important. In the next paragraph of the intro (not in the Allotropy section) we can follow with the second definition which is often described as isotopically pure.Dirac66 (talk) 02:11, 14 August 2013 (UTC)

Astronomical Californium[edit]

In Description

Cf-254 has been detected in supernova IC-4182 during 1956. ref. "Californium-254 and Supernovae" Burbidge et. al. in Phys. Rev. 103, 1145 (1956) URL: DOI:10.1103/PhysRev.103.1145 (talk) 19:10, 14 February 2010 (UTC) darianjenkins at googlemail

I am suspicious because the Cf-254 identification was done merely by the lifetime of 55 days - too weak an argument to me. Materialscientist (talk) 23:29, 14 February 2010 (UTC)

Why not astronomical Curium?[edit]

If californium is detected in supernova, presumably there should be curium which is a lighter element. The alpha decay of Californium can also produce curium. It is interesting to note that the half lives of primordial Pu-244 (8.0 * 107a) and Cm-247 (1.67 * 107a) are comparable.Anoop.m (talk) 17:59, 6 March 2011 (UTC)

Look at the date on that paper! This is 55-year old data which is now believed to have been misinterpreted. It is now thought that supernova light curves are driven by the decay of 56No and 56Co, not 254Cf. Check and references therein. — Preceding unsigned comment added by (talk) 07:14, 8 January 2013 (UTC)


In the section on history it states that the term "element" was originally used to refer to states of matter. It goes on to list the relevant elements and their associated states of matter: solid/earth, liquid/water, gas/air, and plasma/fire. I don't believe that this statement is accurate. The original Classical elements were devised in ancient times (roughly Hellenistic era), but plasma wasn't discovered until the 19th century. The connection is tenuous. (And tt sounds like new-age hokum to me.) I think the first part of this section should be changed or removed completely. Danshil (talk) 15:58, 5 July 2010 (UTC)

I agree. It's quite plausible that the names originated from natural observations of phases of matter (clearly not plasma, except the sun and stars) however, the philosophical theories weren't equivalent to phases of matter. Once aether was no longer needed for celestial mechanics, the name was reused, sometimes in connection with odic force but most recently as the luminiferous aether. But that's TMI for this article.
I took out the global statement saying "they're all the same" because they're only similar due to everyone living on the same planet observing the same phenomena. There actually were theoretical differences. The classical elements article is able to compare and contrast the various theories but, again, that's TMI here and Greek philosophy is the proper basis for comparison for history of science. Thanks—Machine Elf 1735 (talk) 18:13, 5 July 2010 (UTC)
Concur just to put down a note: the peripatetics with Plato, Aristotle and a couple of other guys imagined that every element was composed from thingies that looked like the platonic solids, of exactly five kinds. They imagined that the triangles were kind of abstract "atoms", rejecting the more modern-looking atomism of Democritus. The elements "water", "fire", "earth", "air" and "ether" was nothing like "states of matter", they were more like the essence of their respective practical manifestation if such a weird thing can be imagined these days. Rursus dixit. (mbork3!) 12:04, 21 March 2011 (UTC)
Er, peripatetics (as opposed to "academics") were connected with Aristotle's school at the Lyceum (as opposed to Plato's Academy).
Aristotle rejected Plato's quasi-atom interpretation, which was no-doubt inspired by the Pythagoreans. Aristotle thought triangles were abstractions, and while they composed abstract "solids", they could not be said to compose real substance. Aristotle was ever-so-much more the materialist than Plato, although the atomists, in general, were strictly materialist (and Plato isn't counted among them, except to mention his solids in connection with the elements).
Aristotle gave an entirely different account of the transformation between the elements, (the change between "states of matter", coupled with cosmogonical considerations and a general explanation of what it means for something to change). Aristotle's hylomorphic reinterpretation of Plato's theory of forms implied the elements can't exist in pure form because they're intended to account for prime matter (and matter cannot exist without form). Form, for Aristotle, is an abstract description of something, entirely "before" or entirely "after" whatever change is being discussed.
The elemental forms were thus abstractions of "a potential to do work", that of heating or desiccating, which are always a "mixture" as found in nature (in various ratios). So abstractly, fire is what's hot (but dry), air is what's moist (but hot), water is what's cold (but moist), and earth is what's dry (but cold).
Aristotle was concerned to eliminate the possibility of an indeterminate form (some intermediate state) during an elemental transformation. His solution was similar to Gray code in modern communication and computing, multiple "contrarieties" don't undergo change simultaneously: for example, fire can't change directly to earth, the change must be analyzed as two stages: either fire→air→earth or fire→water→earth.
Anyway, selective accounts of Democritus (notably Bertrand Russell's A History of Western Philosophy) are tenuously "modern-looking", but a string of lucky guesses are impressive in a way even Aristotle would have characterized as non-scientific.—Machine Elf 1735 08:22, 22 March 2011 (UTC)

Elements found in nature[edit]

There are several different numbers of elements occuring naturally in nature that are thrown around on this page. Could we reach a consensus on the correct amount? -- (talk) 03:29, 22 August 2010 (UTC)tytyytytytytyty

Did you read it carefully? Give an example of a discrepancy (making sure you're not giving example of what are different figures for what are actually two different things) SBHarris 17:26, 28 February 2011 (UTC)
He might have been right in 22 August 2010: there were mentionings of the speculative discoveries elements 122 and 126, at that time that a small minority of physicists believed could be factual. Those alleged discoveries were later retracted so now it is almost universally 118 elements (or less), where 117 is the latest plausible discovery. In other words: we've gotten the numbers right now. Rursus dixit. (mbork3!) 12:16, 21 March 2011 (UTC)
Nothing like 118 elements are found in nature. 94 elements are found in nature-- the rest are made artificially, with increasingly small half-lives. Saying element 118 is found in nature is like saying automobiles are found in nature. That isn't what we mean by the phrase in English.SBHarris 16:35, 21 March 2011 (UTC)

These numbers seem to conflict. If they don't, then the writing is not clear enough for a lay reader. "As of 2010, there are 118 known elements .... Of these 118 elements, 98 occur naturally on Earth." "Of the 94 naturally occurring elements, those with atomic numbers 1 through 40 are all considered to be stable isotopes."

And these as well: "As of 2010, there are 118 known elements ... The first 98 elements have been detected directly on Earth as primordial nuclides present from the formation of the solar system, or as naturally-occurring fission or transmutation products of uranium and thorium.... The remaining 24 heavier elements, not found today either on Earth or in astronomical spectra, have been derived artificially." — Preceding unsigned comment added by (talk) 04:03, 6 March 2012 (UTC)

Last week this edit removed 6 elements from the list and changed the total to 92 in part of the article, although the Description section still says 98. I suspect 98 is correct but I am not certain. Could someone please check this out and restore consistency and correctness? Dirac66 (talk) 00:11, 28 June 2014 (UTC)

Emsley in Nature's Building Blocks says that 5 isotopes of Cf are detectable in U deposits. See This reference is also used in the californium Wiki article. But 98 is the highest we see today on Earth, as 99 and 100 require the r-process with 15 and 17 rapid neutron captures, so you only see them in operating reactors, H-bomb detonations, etc. They may have been made in the natural Oklo reactor, but are all gone now (not detectable). So 98 is correct. I'll just lift the Emsley ref from the Cf article, and put it back the way it was. BTW, "primordial" means since the beginning of the solar system, not since the Big Bang. Be, B, and Li are cosmogenic AND primordial. SBHarris 01:36, 28 June 2014 (UTC)

Thanks for clarifying and for fixing the intro section. I have also fixed the Occurrence and Origin section to be consistent, by reverting the edit I mentioned from last week. Dirac66 (talk) 22:29, 28 June 2014 (UTC)

Table summarizing origin of elements?[edit]

Would it be useful to augment the information in element table within this article with a new column showing the origin of the element (big-bang, stellar, supernova, etc)? Perhaps augment the primordial/transitory/synthesis column? Or an additional column? See Nucleosynthesis, Big Bang nucleosynthesis, Stellar nucleosynthesis, and Supernova nucleosynthesis. This article already has an "Origins" section which discusses these origins in general terms, but I was looking for a tabular summary, per-element. --Noleander (talk) 20:15, 7 July 2011 (UTC)

After studying the "List of the 118 known chemical elements" table, I propose to implement the above suggestion by changing the entries in the "Occurrence" column by replacing "primordial" entries with three more specific choices: Big Bang nucleosynthesis, Stellar nucleosynthesis, or Supernova nucleosynthesis. If unknown, I could just leave it as "primordial" or perhaps "nucleosynthesis". The "Transitory" and "Synthesized" entries would not be changed. Comments? --Noleander (talk) 03:39, 8 July 2011 (UTC)
I find this table and accompanying text unsatisfactory on several levels. Firstly it contradicts the introduction on the origin of lithium, beryllium and boron. Secondly it (and the intro) imply that all hydrogen and helium is of primordial origin, and do not allow for the Stellar nucleosynthesis of helium which is still happening in most stars, including our sun. Furthermore, lithium to boron are referred to as primordial with a spallation origin. This is logically nonsense, since spallation requires a pre-existing heavier element such as carbon, which according to the article derives from stellar nucleosynthesis, i.e. NOT primordial. Much more clarity is required here. The most serious fault is the implication that elements heavier than hydrogen are not still being produced currently. Plantsurfer (talk) 10:52, 18 May 2013 (UTC)
The column heading should be Origin (how it was formed) rather than Occurrence (how much is found now and where). Noleander's breakdown of primordial into 3 categories is a good idea, but we should also add cosmic ray spallation. Also the data for each element can include more than one origin in order of estimated importance. For He, Big Bang first, then stellar nucleosynthesis. For Li, Big Bang then cosmic ray spallation. And so on. Dirac66 (talk) 21:58, 18 May 2013 (UTC)

Error in atomic masses?[edit]

this is error right? "the atomic weight of chlorine-35 to five significant digits is 34.969 u" "relative atomic mass of chlorine is 35.453 u" if yes please fix it, somebody. — Preceding unsigned comment added by (talk) 20:05, 1 May 2014 (UTC)

The two values are both correct but they refer to different things. Chlorine has two stable isotopes - chlorine-35 and chlorine-37. The value 34.969 is the mass of chlorine-35 only. The value 35.453 is the weighted average of both isotopes, and is closer to 35 than to 37 because there is more Cl-35 than Cl-37. This is all explained in the section Atomic mass and atomic weight. Dirac66 (talk) 20:46, 1 May 2014 (UTC)
I looked here the Relative Atomic Mass and Standard Atomic Weight of chlorine-35 and it was 34.968 852 68(4) and 35.453(2), respectively, unlike in quotations I pointed above. I mean here "relative atomic mass of chlorine is 35.453 u" must be 34.969 and here "the atomic weight of chlorine-35 to five significant digits is 34.969 u" must be 35.453. Lufnuf (talk) 22:33, 1 May 2014 (UTC)
and instead of "atomic weight of chlorine-35" must be chlorine without number and chlorine-35 here "relative atomic mass of chlorine is 35.453 u"

I think that part of article (Atomic mass and atomic weight) must be revised. Lufnuf (talk) 23:56, 1 May 2014 (UTC)

The layout of the link is a little confusing. The values in the columns Relative Atomic Mass and Isotopic Composition refer to individual isotopes (such as Cl-35), but the values in the column Standard Atomic Weight refer to an average for the element (such as Cl). That is why this column has only one value for each element. If you click on the words Standard Atomic Weight at the top of the column, you will find the NIST explanation, starting with the words: The relative atomic mass of an element is derived by averaging the relative atomic masses of the isotopes of that element. So the values are both correct.
I do however now see some changes which may make this section clearer. The title Atomic mass and atomic weight wrongly suggests that the difference between mass and weight is important here. I will change it to Isotopic mass and atomic mass in order to emphasize the important difference between the two values such as Cl-35 and Cl. All the values are now considered as masses, so we only need to mention once that weight was used historically. And finally I will place this section after the Isotopes section, since we should define isotopes before talking about them. Dirac66 (talk) 02:38, 2 May 2014 (UTC)

List of 118 known elements[edit]

Hydrogen has a description of being non-metal but it has under large amounts of pressure it has metallic properties and unproven superconduction. It can be seen on the page "Metallic hydrogen". It probably won't fit in the box so i think it should write "metal[1] and non-metal" and at [1] is written: Under pressure of 300 GPa and higher hydrogen liquifies and has metallic properties. See more at:"Metallic hydrogen"

X mark.svg Not done having some "metallic properties" does not necessarily make it a metal.
Moreover, it is one of the "Other elements occasionally are classified as metalloids" - in the metalloids article. As it is not even regularly defined as a metalloid "a chemical element with properties in between, or that are a mixture of, those of metals and nonmetals" - It cannot jump that hybrid class straight into being a metal. - Arjayay (talk) 14:31, 11 June 2015 (UTC)
Perhaps the heading should read Description at STP, just as the third last column specifies State at STP. It is true that the properties of hydrogen (and many other elements) change drastically at sufficiently different pressures and temperatures. Dirac66 (talk) 15:15, 11 June 2015 (UTC)

Semi-protected edit request on 9 July 2015[edit]

I suggest reverting the first paragraph to the last version by Materialscientist. The current version is confusing - the two definitions of an element offered are identical, and there are also spelling and grammatical errors.

Ninebelowzero (talk) 18:23, 9 July 2015 (UTC)

Yes check.svg Done -- Orduin Discuss 19:01, 9 July 2015 (UTC)
@Orduin and Ninebelowzero: That edit was discussed on WikiProject Chemistry, and the definitions are sourced ... The definitions are absolutely not identical. TomT0m (talk) 18:42, 11 July 2015 (UTC)
For the discussion, please see: Wikipedia_talk:WikiProject_Chemistry#Chemical_element_:_french_and_english_definitionTomT0m (talk) 18:53, 11 July 2015 (UTC)

And for the diff please see : @Plantsurfer, Dirac66, Sbharris, IiKkEe, Neander7hal, and Orduin: So much edit and no reaction on this fundamental definition issue ... Any opinion ? some people on the chemistry wikiproject agreed that the definition of chemical element not as a pure substance but as a type of atom was convenient and relevant. I think it at least should be mentioned in the article.

Sources seem to vary on the definition. As mentioned the IUPAC Gold Book gives 2 definitions: species of atoms and pure substance. One general chemistry textbook (Petrucci, Harwood and Herring, 8th ed. 2002), first (p.5) defines a chemical element as a substance made up of a single type of atom, and later (p.43) explains that atoms of a particular element have the same atomic number or number of protons. Another text (Whitten, Gailey and Davis, 4th ed. 1992) gives a third definition (p.12) as an element as a substance that cannot be decomposed into simpler substances by chemical changes.
My opinion is that giving two definitions of the same word (element) at the outset is confusing, especially if they are called alternative which may suggest (incorrectly) to a reader that one can be more true than the other. Note that IUPAC does not use this word at least. I prefer to distinguish between element and atoms of a given element as per Petrucci et al. As for the definition of Whitten et al., this is the historical definition which preceded the discovery of atomic number, so it does not belong in the intro though it is (and should be) in the historical section. But it does remind us that historically, an element was a large number of atoms rather than a single atom.
So finally my minimalist suggestion would be change the first sentence to two sentences as per Petrucci et al (= possible source):
A chemical element (often just element when the chemical context is implicit) is a pure chemical substance consisting of a single type of atom. Atoms of a given element are distinguished by the number of protons in its atomic nucleus (atomic number). Dirac66 (talk) 21:29, 14 July 2015 (UTC)
P.S. to TomTOm. I don't think your pinging of several people at once worked. I did not actually receive this ping. Dirac66 (talk) 21:29, 14 July 2015 (UTC)
I didn't see the ping either, but no matter. It is difficult, because many "pure" chemical substances do not have a single type of atom. Copper, for one of many possible examples. For this purpose, a definition of what we mean by "type of atom" must come first. An element is a chemical substance in which all of the atoms have the same number of protons in their atomic nuclei. Plantsurfer 22:05, 14 July 2015 (UTC)
We should also be neutral and reflect all the sources, by NPOV principle. (As a side note I came here because I wanted to make precise statements on Wikidata, and the too UIPAC definitions needs actually two Wikidata items, this is an interwiki conflicts). Note that the french article definitly took the Type of atom with a constant atomic number path, which is the definition I prefered, but if the english article take the pure substance one, we will need to link indirectly the élément chimique and chemical element because they would not have the same item (one item, one definition is the necessary rule on Wikidata). It's not a rare case on Wikidata and we have a project to solve such cases d:WD:XLINK the best we can, but it's to be taken into account here (I would not separate the article before a little bit of chatting).
To me the pure substance definition is cumbersome and a relic of the past, when chemists had mainly the substance notion but since now the atom notion has became so important, I think that the substance has become cumbersome and that the real element is the atom, the basics items from which compounds (of elements) are made. Note that the rest of the article is simpler without the substance notion who does not add anything to the isotope notion and so on, and even worse, it's ignored, or confusing, most of the time. ... And that actually a substance is made of ... compounds in the general case. So when we're speaking of elements, it's weird to have an element made of compound.
My opinion would be : use the type of atom definition, mention the substance esewhere for completion and NPOV, with an explanation. I begin to understand however that's it's not really in english speaking languages traditions :/ . TomT0m (talk) 11:34, 15 July 2015 (UTC)
No, of course the definition cannot be restricted to pure substances. Probably, if that is the definition, the element copper has never been observed. Also, it would be logically impossible to discuss elements in the context of alloys, in which they obviously cease to be pure. The word pure is a problem, therefore, but the word substance need not be if we define an element as I did above. Substance does not equate to compound, as you seem to imply. To repeat, An element is a chemical substance in which all of the atoms have the same number of protons in their atomic nuclei.. Plantsurfer 16:44, 15 July 2015 (UTC)
@Plantsurfer: I think we don't understand each other. Take the first definition of the goldbook : A species of atoms; all atoms with the same number of protons in the atomic nucleus.. This means a chemical element is a type of atom with a specific atomic number. This definition as none of the problem mentioned above, it does not need the notion of substance, just of atom. With this definition, the second definitions becomes a pure substance made of a single element. The element/compound relationship becomes, a compound is a type of molecules made of elements, i guess. As molecules are made of atoms, atoms becomes elements of molecules. As molecules are characterized by the type of atoms it is made of, it's characterized by the element (type of atoms) it is made of. As wikipedia is neutral, it has at least to mention this definition, who is radically different from yours. TomT0m (talk) 17:04, 15 July 2015 (UTC)
My definition is identical with that of the goldbook. Plantsurfer 17:11, 15 July 2015 (UTC)
@Plantsurfer: I know but there is TWO definitions in the Goldbook, not only one, this is my problem here :) You don't address that point at all, so it's like I'm talking to a wall :) TomT0m (talk) 17:19, 15 July 2015 (UTC)
@TomT0m:OK, I am not trying to be obstructive, but the fact is my views and yours don't appear to totally coincide. If we combine my sentence and Goldbook definition 1 we get something like An element is a substance consisting of a species of atoms, all of which have the same number of protons in their atomic nuclei. I think that pretty much covers definition 2 as well, and at the same time expresses the definition in a single, neutral, form that coincides with the way most people think of an element. In other words complies with NPOV. An element, in everyday language, is understood to be a substance, not just a single atom, in fact rarely just a single atom, but a single species of atoms of the same type. That type is defined as "having the same number of protons, the same atomic number". Purity is thus implicit in that definition, but crucially, unlike the term "pure substance" is not applied in a way which conflicts with the presence of various isotopes in an element, or with the discussion of elements in the context of mixtures, alloys and compounds. I think it is preferable to arrive at that single definition than to have to rely on messy, multiple sub-definitions that open the door to doubt and uncertainty. Plantsurfer 18:20, 15 July 2015 (UTC)
@Plantsurfer: OK, I think I understand where we disagree. If definition one and definition 2 were equivalent, there would not be two definitions in the UIPAC. I read species as a synonym of type, and an hydrogen atom is an instance of the type Hydrogen. NPOV is not here to reflect what most people would understand, it's here to reflect what authoritative sources says. And the UIPAC is clear : the definition as a type is a valid definition. For example in Wikidata, as I said, this would be expressed as different statement : in the type definition hydrogen is a subclass (knowledge representation) of atoms, all hydrogen atoms beeing instances of hydrogen, while with the substance definition it's a subclass of pure substance (it's what lead me here). We still need the two items however to say that hydrogen substance has part hydrogen atom . If in enwiki this article is about pure substance, fine, but then we would have to unlink (amongst others) the french Wikipedias article, as it is about types of atoms (Un élément chimique est l'ensemble des atomes caractérisés par un nombre défini de protons dans leur noyau atomique translation : a chemical element is the set of all atoms characterized by their atomic number). This would be a little weird though as most of the content of this article is about ... types of atoms, their isotopes, and so on, and that the substance notion is useless. I appears only in the historical section and to distinguish isotopically pure substance from elementically pureone. We could as well focus on the type definition and left substance for history, adding a chapter in history for substance evolving to type of atoms ... TomT0m (talk) 20:01, 15 July 2015 (UTC)
@TomT0m:I have said what I have to say on this, and it is clear that we disagree. I think you are trying to make it all too complicated, and frankly, I am not interested in reconciling our differences with french WP. So what we have to do now is seek the views of other editors and obtain consensus. N'est ce pas? Plantsurfer 20:19, 15 July 2015 (UTC)
@Plantsurfer: If it was just for the differences with frwiki, I guess nobody would have noticed the issue :) but Wikidata is more demanding into definitions, which triggers a lot of cleaning. I had a long discussion because we could'nt reconcile our views with Emw and could not understand each other ... in one cas pure hydrogen substance is an element, in the other hydrogen atom, so we basically have to create for each element two items and link them with has part/part of statements, which is doable, but also split the interwikis for each elements... Maybe enwiki will be directly deconnected with a lot of interwiki links we will have to handle another way, so it's not totally an easy business. I was almost shocked when I had to change the french label of the chemical element(en) item to pure chemical substance made of one element ... Considering the UIPAC had the two definitions, I considered the type one was also a viable option in english this could be an opportunity to just add a word about this on this specific article and consider the main subject was types of atoms, would save a lot of trouble. Actually at least one user on WikiProject Chemistry said he prefered the type definition :)
Anyway, considering the too definitions are valid and sourced, with a solid reference, the least that can be done is to talk about the two definitions on this article. TomT0m (talk) 21:05, 15 July 2015 (UTC)

In other languages ...[edit]

(translated with google translate from other Wikipedias)

Chemical element is the collective term for all nuclides with the same atomic number. => UIPAC def. 1
A chemical element is a type of material constituted by atoms of the same kind => UIPAC 2
Can't really know for sure, but it seems they consider atoms, and atom classification. => I'd say UIPAC 1
chinese too bad translation, they refers to molecules, but ...

In chemistry it is said that two or more atoms belonging to the same chemical element if are characterized by the same atomic number (Z). [1] The atoms of the same element can differ only in the number of neutrons ( mass ). A chemical element can not be decomposed into simpler substances by chemical reactions . The chemical elements are the basic constituents of matter in all its forms. If a chemical substance is constituted by atoms of the same element is called " simple substance "[ no source ], while if it is made ​​of atoms of different elements is called " chemical compound ". Often simple substances are improperly called elements. [1] they speak of this same problem :) => UIPAC 1, with a mention that pure substances are mistakenly called elements, interesting, we're probably not the first to have this dispute :)

portugal (and Brazil?) 

It is called chemical element a set of atoms that have the same number of protons in its nucleus, ie, the same atomic number (Z). The term "chemical element" can also refer to basic elements of matter, which can not be decomposed into simpler substances by chemical methods, that is, indivisible elements. [1] This latter concept is sometimes called elementary substance, differing from the first definition, but often, the same concept is used in both cases.

same as italian.

TomT0m (talk) 21:54, 15 July 2015 (UTC)

Second attempt[edit]

In chemistry, chemicals elements are the basic types of components matter made of atoms, ordinary matter like molecules and other chemical compounds are made of. Elements can be defined of two different ways, but in either way the number of protons in atoms nuclei is used to define elements, called the atomic number, because two atoms with the same atomic number have the same chemical properties. Either it is
* a type of atom with the same number of proton, 1 in the case of hydrogen,
* a pure chemical substance consisting of a single type of atom distinguished by its atomic number[1]
In the first one, we will say that an atom with one proton is hydrogen, or an atom with 2 protons helium, and in the second one we will say that the content of an Hydrogen gaz bottle is hydrogen.

This version is after a discussion with DePiep, who agreed for the change. TomT0m (talk) 17:28, 18 July 2015 (UTC) (also ping @Snipre:)

With the exact same reference. Do you have a consensus to cite that have changed the concensus that was at the time ? TomT0m (talk) 10:17, 19 July 2015 (UTC)
  • TomT0m (talk) (I guess support)) on behalf of Jynto :

    Just my perspective as an English person: the French definition makes more sense.

1. A species of atoms; all atoms with the same number of protons in the atomic nucleus.
2. A pure chemical substance composed of atoms with the same number of protons in the atomic nucleus. Sometimes this concept is called the elementary substance as distinct from the chemical element as defined under 1, but mostly the term chemical element is used for both concepts.
Definition 1 does not entail that the element hydrogen, for example, is necessarily a type in the ontological sense that TomT0m seeks to establish it. Specifically, TomT0m's interpretation seeks to cast "particular" chemical elements like hydrogen as ontological metaclasses, such that one would state "hydrogen instance of chemical element" instead of "hydrogen subclass of chemical element". The former would contradict the way ChEBI (the most widely chemistry ontology) and most chemistry ontologists model elements.
(Aside: TomT0m suggests "a chemical element is a type of atom with a similar atomic number". The atomic number in a chemical element is of course identical, i.e. the same -- not merely similar.)
This thread is spillover from protracted ontological discussions on Wikidata, which I've been party to for years. Complicating the lead sentence (or even lead section) with notes about chemical elements being "types" is unnecessary. The alternatives I've seen proposed in this thread are either garbled and confusing (in line with File:Atom_classes.svg) or ontologically misguided. I think we should keep the "A chemical element is a chemical substance composed of atoms with the same atomic number" wording in the lead sentence and avoid the "A chemical element is a type of atom with the same atomic number". The current definition is ontologically precise, consistent with major scientific ontologies, and simplest to understand for those trying to actually learn more about what chemical elements actually are. Emw (talk) 04:10, 31 July 2015 (UTC)
  • Yes, I'm here because of this dispute, BUT I've been careful to motive everything with reasons outside of the scope of the dispute. The metaclass concept is indeed interesting but not really in the scope.
  • You don't explain at all the first definition of the goldbook who is no less valid than the one CheBi used (and chebi does not have a concept "chemical element" per se : does not returns any exact match, which is a problem for your argument. I think I remember there may be synonyms for this concepts like "elements" in chebi but they are well hidden and contradicts, whatever you think, the first definition of the goldbook.
  • chebi does not give a direct definition for the "chemical element" concept directly in its ontology, and what's that really is of interest for us. It however has a definition for hydrogen atom, which match the first definition of the goldbook : that does not imply substances AND is a type of atoms, and a definition for elements as in the second definition : for elemental carbon. The two are not mixed up.
  • The formulation as "similar" : just change it to identical.*
  • Assuming your interpretation of chebi is correct : Wikipedia is supposed to be NPOV, not to reflect only one, even popular, ontology.
To conclude: Emw here (as he says we discussed a lot but I deny him as the one who is the expert and me in the role of the bad one) has a strict interpretation of the Type-token distinction ontological principle, which lead him to reject the definition of atoms as a type. There is many good reason not to follow him but I don't want to redo the discussion entirely here. TomT0m (talk) 07:50, 31 July 2015 (UTC)
TomT0m (talk) 07:50, 31 July 2015 (UTC)
  • Oppose no version has been proposed that is superior to the status quo definition. I am unclear as to why TomT0m thinks NPOV is being violated here. VQuakr (talk) 20:06, 31 July 2015 (UTC)
    @VQuakr: Because the Goldbook, an accepted reference book, has two distinct definition of "chemical element", and that this article reflects only one of them. That seem to me pretty clear and I don't see any answer to this is this post. I would not consider this vote valid as it ignores the whole point of this proposition. TomT0m (talk) 10:09, 1 August 2015 (UTC)
This is not a dictionary. In this case the concepts both of one specific atom and a group of many instances of that atom can be handled perfectly well with the existing article and lede. VQuakr (talk) 18:44, 1 August 2015 (UTC)
@VQuakr: I disagree. Actually most of the article does not even talk about substances and refers to kinds of atoms and thier properties. So no, the introduction and the rest of the article does not match and the "type of atom" definiton is not clearly stated although its the most useful in the rest of the article. This is actually confused and a bad covering of the topic, some thing remains implicit. If we were talking of substances, it would be said that diamond and graphene are the same element, although they are very different. Talking of atoms we get rid of a lot of problems such as substance purity to focus on atom propertis (stability, …), and that's actually what this article does. A proof amongst other : I can read in the introduction : "When distinct elements are chemically combined, with the atoms held together by chemical bonds, they form chemical compounds." Look at the defintion of chemical compounds : a molecule is a chemical compound. And a molecule is not a susbstance. Suubstances are made of molecules. The definition used in that senstence is ergo more likely to be «kind of atoms», as molecules are made of atoms, not of sustances. So the definition given is inconsistent with the rest of the article. TomT0m (talk) 19:14, 1 August 2015 (UTC)
The next sentence : «While about 32 of the chemical elements occur on Earth in native uncombined forms, most of these occur as mixtures.» If an element is a pure substance, then its a contradiction that it occurs as a mixture ! This article is fighting its own definition problem. However its not at all a contradiction that types of atoms occurs in mixtures. They don't have a purity problem. Purity is cumbersome … so why putting an emphase on it ? TomT0m (talk) 19:43, 1 August 2015 (UTC)
The answer to your question is that we don't. The definition used in this article avoids the word "pure", use of which leads to more than one kind of ambiguity. Plantsurfer 20:33, 1 August 2015 (UTC)
@Plantsurfer: If the substance is consisting of atoms of the same number of protons … then how can it be unpure ? There is way too many unsayed here.
Your argument is so poorly stated that I am not clear whether your objections are ontological or linguistic. Either way, I still oppose rephrasing the lede into a confusing word salad. VQuakr (talk) 22:45, 1 August 2015 (UTC)
@Vquakr: please don't blame me for your own confusions :) I'd better you explain me how the examples are given are consistent, I clame the opposite. I clame this is a linguistic mess because of an ontological one. One term is used one time with one definition, one other time with another. But it's not said … And answer my objections (I just noticed the first topic on this page in 2010 is already about this subject … this must be solved.) I don't care if it's my wording or if it's rewritten, this just can't stay as is. TomT0m (talk) 06:40, 2 August 2015 (UTC)
As the editor proposing a change, the onus is on you to present a better option alongside your coherent reasoning. You have done neither, hence my opposition to the proposed change. VQuakr (talk) 07:33, 2 August 2015 (UTC)
I'm not a native english speaker so it might be that some other are better than me to write clearly. What I know is that the UIPAC definitions are clear as a stream water and rock solid and that I propose changes to align with them since forever, first at the WikiProject, in which I gained support from some Wikipedian, then here, but I seem only to gain unconstructive opposition here … Seriously I'm trying very hard to explain what's wrong here, I'm shocked you present this as MY reasoning as you just don't ackoledge what the sources says. There is two definitons for a reason. I'm just trying to explain that. I'll quote a comment of 2010 in this very same page I have nothing to do with : "I've always thought that a chemical element is a... er... totality of atoms with the same number of protons/same atomic number" (Adnyre … 2010) so I'll reject any kind of personal arguments. Is this quote still too complicated for you, you don't understand it either ? TomT0m (talk) 07:49, 2 August 2015 (UTC)
Please review WP:DICTIONARY. It is not unconstructive to state that the current lede is better than any alternatives presented so far. In this case, the two definitions are so similar that there seems to be little need to explicitly state both. VQuakr (talk) 08:31, 2 August 2015 (UTC)
@VQuakr: Sorry, but I'll ask you (again) to try to understand my points. Elements are supposed to be the basics other stuffs are made of. In the past chemists used substances, which lead them to consider substances to be this base. With basic substances, they built compound substances. Now our ideas are more clear : compound substances are made of molecules, and it's simpler to consider compounds not as substances, but as simpler stuffs like molecules. It's the choice chemical compounds make. Then elements has to be atoms to be consistent, as an «element/compound» relationship is usally supposed to mean that compounds are made of elements. We get rid of the whole «substance» notion which is barely useful in the rest of the article, so useless and cumbersme, to a simpler definition. For the sake of completeness we cite the other definition and add a word about this in the history definition. Can we agree about that first ? I don't want to lose my time writng stuffs that will be reverted anyway on gibberishness justification when something else it at sake. TomT0m (talk) 09:13, 2 August 2015 (UTC)
Oppose. This synthesis strays further and further from the sourced definition. Let me counter this with the following observation: Chemical element is intrinsically a collective concept. Using the IUPAC Goldbook definition (whichever one, take your pick), it consists of atoms (note the plural) with the same atomic number. We do not think of an atom as an element, we refer to it as an atom of an element. The definition we have arrived at in this article is totally consistent with the sourced IUPAC definitions. It is probably the most concise and compact statement of the concept that the English language will allow. There comes a time when these endless, long, rambling, ultimately unproductive discussions must come to an end, when we have to put up or shut up. We have work to do elsewhere to improve this and other articles. If you think you have arrived at a form of words that improves on the first sentence of the lead, then please feel free to post it here for all the editors to consider. Otherwise we need to close this discussion now and move on. Plantsurfer 10:00, 2 August 2015 (UTC)
@Plantsurfer: This is no contradiction. The first one is (mathematically) a «definition by intension» of the set of all atoms of some element. The second one is a definition of sets of substances. While the first one defines sets of atoms, the second one defines sets of substances … This is a fundamental difference this article does not explain at all, and even choose to ignore, in favor of the definiton of the set of substances. Do you ralize that children often learns the «the set of all atoms with some atomic number», that this definitiomn is actually used in chemical compound and is ignored here ? This is a fundamental question. As I said, if we do not agree of that, anything I could propose will be rejected so I don't know why I should care to … TomT0m (talk) 10:22, 2 August 2015 (UTC) Oh, the article has been rewritten since I last …and it seems I was wrong. TomT0m (talk) 11:30, 2 August 2015 (UTC)
  • Oppose Goldbook provides two definitions which have only the subtlest difference in meaning, and adds to the second ". . . but mostly the term chemical element is used for both concepts", thus acknowledging that the two are essentially coterminous. The definition given in the article is a clear statement of the substantive points. There is no need for further elaboration here. The Goldbook citation is provided, and any reader can refer to what is said there.Plantsurfer 10:48, 1 August 2015 (UTC)
    but mostly the term chemical element is used for both concepts" It's used for both concept but this article would only define one of the concepts ? This sounds confusing to me for ther reader if someone use it in the non wikipedia sense and he hears the wikipedia one.
    The definition given in the article is a clear statement of the substantive points.
    Can your rephrase ? I don't understand.
    The Goldbook citation is provided, and any reader can refer to what is said there. No. It's to wikipedia to reflect the sources. Choosing a definition other one clearly accepted one is an is an emphase of one definition and a clear hiding of the other one, hence a violation of the NPOV policy. TomT0m (talk) 11:43, 1 August 2015 (UTC)
And please stop pinging people. This is an open discussion, and pinging people makes it personal, verging on trolling.Plantsurfer 10:48, 1 August 2015 (UTC)
Sorry but I don't share this point of view at all. When I reply to someone arguments I notify him, seems to me the least I can do ... TomT0m (talk) 11:43, 1 August 2015 (UTC)


The Description section states confidently "Of the 98 naturally occurring elements, those with atomic numbers 1 through 40 are all considered stable." However, as we know from the potassium article, "Traces of 40 K are found in all potassium, and is the most common radioisotope in the human body." and the product of its decay, Argon, continues to accumulate in earth's atmosphere. Carbon also has a naturally-occurring radioisotope. Some clarification is therefore needed. Plantsurfer 14:27, 13 July 2015 (UTC)

I have now tried to improve this section. To start, I have the changed the mention of stable elements (=??) to stable isotopes (= no observed radioactive decay). Dirac66 (talk) 02:05, 14 July 2015 (UTC)
Dirac66: Thank you for your edits to this Page, including your edits of my edits. All are definite improvements. Regards, IiKkEe (talk) 15:36, 19 July 2015 (UTC)
K-40 has mass number 40 but an atomic number of 19, and is unstable only because it's an unstable isotope of an element that generally is stable only at mass numbers of 39 or 41. What the article means is that elements with atomic numbers 1 through 40 (ie hydrogen to zirconium) have at least one stable isotope that is theoretically stable, with no way to decay to anything else by some other possible process. Above 40, this isn't true, and even stable isotopes that have never been seen to decay are theoretically unstable to decay by alpha decay, spontaneous fission, double beta decay, and so on. I would have thought anything over iron and nickel (Z = 26 and 28) would be theoretically unstable to decay back toward those elements, but apparently mechanistic considerations inhibit all processes until you get to Z = 41. No, I don't have a reference. SBHarris 23:25, 31 July 2015 (UTC)

Definition of chemical element[edit]

To IiKkEe: Stille someone who edits the article without commenting on the definition issues ... I'm really frustrated /o\

Did you read the discussion about the concurrent definitions of the GoldBook on talkpage ? What do you think about this ? TomT0m (talk) 11:43, 17 July 2015 (UTC)

I am not clear what you are saying in your first paragraph, or what you are asking me in the 2nd. And to what edit of mine are you referring? Please elaborate. Regards, IiKkEe (talk) 15:29, 19 July 2015 (UTC)
The goldbook defines chemical elements either as types of atoms, or as chemical substances. The article currently only reflects the second definition, which is definitely not the most modern. I made an edit on chemical element to mention the two definitions, it was reverted. As I fear this will happen again, I'm trying to build a concensus before retrying. The discussions are all on the article talk page. What do you think about this issue ? I'm here because, as you're one of the most recent editors of the article, you might be interested into this discussion. TomT0m (talk) 15:38, 19 July 2015 (UTC)
Thank you fro your prompt reply. So as I understand, you have no objection to any of my edits, you are simply alerting me to the discussion about the definition? If so, thank you for the courtesy. At this point, I do not have the expertise to take part in the debate, but will certainly follow it. And please give me feedback on any of my edits that you may be frustrated with. Regards, IiKkEe (talk) 15:53, 19 July 2015 (UTC)
No I did not notice anything (except you edited on the introduction and that's where I did want a change :) ) . I don't really have any expertise below what I put on the different talking about this issue. What I know is that an earlier version of the article was like I want it to be and that the arguments of those who don't want the change are weak : "the definitions are the same" incorrect. "it's too complicated" => that's what the sources says. The current version does not even explain elements are the basics of our matter. That's the definition used in many other Wikipedia. I don't understand why one would want to remove one legitimate and sourced definition. It's a violation of the NPOV policy. TomT0m (talk) 16:39, 19 July 2015 (UTC)
Could you give me the date and time from the "Edit history" which reflects what you want the Lead to say? I'll be glad to take a look: maybe I will have an opinion! Regards, IiKkEe (talk) 17:46, 21 July 2015 (UTC)
  1. I found this version (April 2009) who seems perfectly fine to me in the introduction and mentions the two definitions.
  2. This is the version I proposed following the discussion I started on Wikipedia:WikiProject Chemistry, probably imperfect but just talking was not enough to make things move so I included it after a few days when nobody reacted :
  3. In chemistry, chemicals elements are the basic types of components matter made of atoms, ordinary matter like molecules and other chemical compounds are made of. Elements can be defined of two different ways, but in either way the number of protons in atoms nuclei is used to define elements, called the atomic number, because two atoms with the same atomic number have the same chemical properties. Either it is
    * a type of atom with the same number of proton, 1 in the case of hydrogen,
    * a pure chemical substance consisting of a single type of atom distinguished by its atomic number[1]
    In the first one, we will say that an atom with one proton is hydrogen, or an atom with 2 protons helium, and in the second one we will say that the content of an Hydrogen gaz bottle is hydrogen.

This is the version I'm proposing on the article talk page for inclusion. Was dejargonized after a discussion with depiep.

I'm mostly interested here in the fundamental definitions. My personal preference would go to a version with the first definition of the goldbook as it's more modern and imho drops the substance stuff who do not serve any purpose in the rest of the article, or worse is even confusing, (and it would ease the work on Wikidata and interlanguage link, but that's not the fundamental issue :) ), but it does not seem to be the definition children learns in english speaking countries, which may be the root of the problem. I'd be happy with any version that mentions the two definitions. TomT0m (talk) 08:39, 22 July 2015 (UTC)
The above is a thoughtful discussion which I believe belongs not only here but also on the Chemical element Talk page. I will paste it there, and will respond to your thoughts there within a couple of days. Regards, IiKkEe (talk) 20:39, 24 July 2015 (UTC)