Talk:Periodic table

Natural occurrence of transplutonium elements

Have any of americium, curium, berkelium, or californium ever actually been detected in nature? I can't find any source besides Emsley that claims they do exist naturally, and as far as I can see, he claims that they are formed naturally in minute quantities by neutron capture in concentrated uranium ores but does not cite any source claiming to have detected them. I certainly find it plausible that he's correct, but if there haven't actually been any detections of natural transplutonium elements, should we be making that claim? - Bootstoots (talk) 18:24, 6 May 2015 (UTC)

(Replying here, instead of the individual articles...)

I added this in the first place, when the book was new, and I therefore trusted that he had actual studies backing this up (annoyingly he does not provide a detailed list of sources). Since then, though, I haven't found a source for anything beyond Pu being natural.

Also, it's not very plausible in the first place. Since the ²³⁹Pu:U ratio in nature is on the order of 1:10¹¹, we can roughly assume that each atom in a uranium deposit today has about a 10⁻¹¹ chance of capturing a neutron. This factor multiplies up very quickly, so that by the time we get to Bk and Cf we have not even one atom left (and this doesn't even factor in decay). The resulting values for Am (≈10⁻³³ mg/kg) and Cm (≈10⁻³² mg/kg) are at least physically possible, but when we consider that it results in picogram quantities of these elements, the possibility of detection falls straight into the abyss.

TL;DR: we should get rid of all of these statements about natural transplutonium elements ASAP. Double sharp (talk) 08:34, 7 May 2015 (UTC)

I think your numbers are off: If it takes 3 neutron captures to produce Am and 4 to produce Cm, you'll get 10⁻²⁷ mg/kg for Am and 10⁻³⁸ mg/kg for Cm. But your point stands that detection would be practically impossible with these proportions. Still, I'd hesitate to discard Emsley's claims based on these calculations unless the claims are also disputed in more recent sources of comparable (or higher) reliability as Emsley's book; it's hard to believe Emsley just made them up. It's conceivable that neutron capture is more likely than 1:10¹¹, or that the transplutonium elements are naturally produced by other (posibly more likely) mechanisms than multiple neutron capture, e.g. by capturing alpha particles from the uranium decay. --Roentgenium111 (talk) 11:17, 7 May 2015 (UTC)

Oops. (To make matters worse, these slightly OR-ish figures are in List of elements – although for Cm I was looking at the double beta decay from ²⁴⁴Pu, which actually seems to be more likely than the quadruple neutron capture: I don't trust my figure for that anymore, so you'll have to check it out.) The point stands, though. (And I'll fix my figures!)

I haven't seen anyone else even mention these claims at all, although as with Tc, Pm, Np, and Pu, it may take some time for them to become widely accepted. (And if the natural ²⁴⁴Pu detection is itself controversial, one wonders how much credence one should give to a single experiment finding transplutoniums.)

It is hard to believe though that Emsley would make things up. He explicitly mentions neutron capture as the mechanism for producing these transplutoniums, although as you note alpha particle capture would be more efficient and perhaps more likely.

Also, why does Emsley list ²⁵³Cf as natural but not its daughter ²⁵³Es? If there has been an experiment showing the existence of natural ²⁵³Cf that didn't have the sensitivity to detect ²⁵³Es (which is the most obvious explanation), one would think that it would be findable. But I have not yet found such an article, years after it should have appeared if Emsley could draw on it for his 2011 book. Double sharp (talk) 13:00, 7 May 2015 (UTC)

Has anyone considered contacting Emsley? He may provide us with some data he has and we don't. His Twitter account is easy to find (and it's active), and his email is also findable (although I cannot tell if he checks it nowadays). I may do it myself when I am in front of a laptop and have enough time to do that.--R8R (talk) 13:06, 7 May 2015 (UTC)

Yes, the einsteinium omission is strange and puts another shadow of a doubt on Emsley. But you wrote in Talk:List_of_elements#Abundances_for_the_really_rare_elements last year that you had found corroborating sources for Am and Cm at least? --Roentgenium111 (talk) 13:22, 7 May 2015 (UTC)

Yes, but they were really lousy ones, posted earlier on this talk page a while ago (and the links don't work anymore, although I recall them working and stating Am as natural): the discussion is copied at Talk:Americium#Natural?. I'd much prefer a published paper, which is where this sort of info would most likely be first disseminated. As for Cm, it's a very reasonable inference from two published facts: (1) ²⁴⁴Pu is natural and (2) ²⁴⁴Pu can undergo double beta decay to ²⁴⁴Cm. Double sharp (talk) 14:41, 7 May 2015 (UTC)

Thanks, I forgot the old discussion. Your Cm inference seems reasonable, but note that the natural existence of Pu-244 has apparently been put into doubt by a newer search (J. Lachner et al. Attempt to detect primordial ²⁴⁴Pu on Earth. Phys. Rev. C 85 (2012) 015801. doi:10.1103/PhysRevC.85.015801), and that Pu-244 is not in our list of known double-beta-decay isotopes. --Roentgenium111 (talk) 12:46, 12 May 2015 (UTC)

Hmm, that's interesting about ²⁴⁴Pu. We'll probably have to mark it as disputed somehow, then (although it would still be "from decay" even then, as I think natural ²³⁹Pu is pretty uncontroversial).

²⁴⁴Pu does appear to be not in our list of known double-beta-decay isotopes, but a very rare double beta decay mode (7.3×10⁻⁹%) is listed at Isotopes of plutonium and cited to [1] (which unfortunately requires registration, so I can't check it). I also found this source describing a 1992 experiment that found the double beta decay of ²⁴⁴Pu to ²⁴⁴Cm (with partial half-life ≥1.1×10¹⁸ years), so I think that's solid. I've added ²⁴⁴Pu to the table in double beta decay on that basis. Double sharp (talk) 13:20, 12 May 2015 (UTC)

As I understand it, Moody et al. did not observe Cm production: "We saw no evidence of Cm activity in any of the three samples." Thus they could only give a lower limit on the half-life. --Roentgenium111 (talk) 15:21, 12 May 2015 (UTC)

Oh, you've read the article? That's really strange, since the abstract posted says "We have searched for the ingrowth of ²⁴⁴Cm in a 1.45-g sample of ²⁴⁴Pu. We isolated a curium fraction after an ingrowth period of 1.03 yr; during this time the ²⁴⁴Pu sample produced ≤0.24 alpha disintegrations per day of ²⁴⁴Cm (95% C.L.), corresponding to a half-life for the double beta decay of ²⁴⁴Pu of ≥1.1×10¹⁸ yr", which seems to imply that they did see the double beta decay (as ²⁴⁴Cm is stated to have been isolated). I can't imagine they would make such a claim in the abstract if they didn't actually see it. Unfortunately I can't access the fulltext, which would definitely be illuminating. Double sharp (talk) 14:44, 13 May 2015 (UTC)

I can access it from my university account, but I haven't read it completely. Apparently the Cm detected was from contamination by a commercial Pm tracer, but the abstract (and the article) is indeed worded ambiguously. Logically, a zero result is also "≤0.24 alpha disintegrations"... --Roentgenium111 (talk) 15:17, 13 May 2015 (UTC)

A veritable masterpiece of ambiguous writing! I've taken ²⁴⁴Pu back out of double beta decay, then. Although what to make of the cite at isotopes of plutonium, then? From memory (before it needed registration) it was pretty much your average online chart of nuclides, listing decay modes among other things: so the question is where they got ²⁴⁴Pu double beta decay (and the figure) from. Given this situation, we should probably not even mark Cm as "from decay", then. Double sharp (talk) 15:48, 13 May 2015 (UTC)

I wrote an e-mail to John Emsley to ask him where he got the info on the natural occurring transplutonium elements. John was very kind and helpful when I contacted him last time on issues with the discovery of helium. --Stone (talk) 20:31, 7 May 2015 (UTC)

Eagerly awaiting his response! Natural transplutonium elements are very cool. Double sharp (talk) 15:02, 8 May 2015 (UTC)

John says that most of the info on the radioactive elements originated from mail exchanged with Walter Saxon a consultant for Oxford University Press in New York. Would be nice to know a little more about him. --Stone (talk) 20:02, 12 May 2015 (UTC)

He's indeed rather hard to find on Google. I'm still inclined to remove mention of natural Am, Cm, Bk, and Cf from the main periodic table, because the only source seems to be Emsley who got his info from Walter Saxon, and there's no other corroborating paper. We could still leave it as something like "Naturally occurring Am, Cm, Bk, and Cf has been reported, but not confirmed", I guess. (And to everyone who was wondering about that: yes, that makes astatine regain its position as the rarest natural element!) Double sharp (talk) 15:52, 13 May 2015 (UTC)

Semi-protected edit request on 19 May 2015

In the section 3.1 "Electron configuration", there is a line saying:

  "The electron configuration for neon, for example, is 1s2 2s2 2p6. With an atomic number of ten, neon has two electrons in the first shell, and eight electrons in the second shell"

Which is incorrect, as in about the middle of said line, it says "eight electrons in the second shell", whereas neon actually has six electrons in the second shell, which is also stated in the next sentence "two in the s subshell and six in the p subshell".

Please change this to be correct, as it confused me a little bit, and it may confuse others in the future.

NewGarbo (talk) 05:33, 19 May 2015 (UTC)

Second shell contains s and p subshells together. Look at numbers before the letters in configurations, they represent shells. 2 in this case represents that they're in second shell. So the article info is correct and no changes were needed. PlanetStar 05:52, 19 May 2015 (UTC)

"Periodic" table

"Although precursors exist, Dmitri Mendeleev is generally credited with the publication, in 1869, of the first widely recognized periodic table." I'm not an expert but I guess this is wrong. The periodic table is based on the periodic law which Mendeleev discovered, right? So all other tables before were systematic tables but not periodic tables. — Preceding unsigned comment added by Wolk777 (talk • contribs) 13:48, 12 June 2015 (UTC)

Did not, for example, John Newlands produce a precursor with periodicity indeed? -DePiep (talk) 15:28, 18 June 2015 (UTC)

Hmm, ok. I meant it was "part periodic", not the same as the modern periodic table. — Preceding unsigned comment added by Wolk777 (talk • contribs) 17:23, 20 June 2015 (UTC)

Would "Although less coherent precursors exist" do? Sandbh (talk) 23:56, 20 June 2015 (UTC)

Edit request 20 June 2015

I would like to add following link to "See also" section:

• Interactive periodic table

 Not done that is a promotional site, promoting its advertisers. - Arjayay (talk) 21:11, 20 June 2015 (UTC)

Periodic Table (of Elements?)

I was a bit bothered and confused by the title of the page. A periodic table is merely a type of table design, so this one should be, and generally is, called the Periodic Table of Elements. Not wanting to appear ignorant, I came here first, since surely I can't be the first of this opinion, and the matter must have been settled before. What is the reason for the shortened, generalized title? Surely "Periodic Table" could just redirect to "Periodic Table of Elements", and the disambiguation is plainly clear.

In addition to this, perhaps a page should be created for the sort of table itself, with a link to the Table of Elements. — Preceding unsigned comment added by Zekava (talk • contribs) 23:25, 6 July 2015 (UTC)

From my experience, "periodic table" is the most common name for the table (when it comes to English. Say, in German, they usually speak about the "periodic system of elements"), hence the title for the article. Plus, it's just simpler, and when people talk about a periodic table, they usually mean the one that orders chemical elements ("It is the greatest happiness of the greatest number that is the measure of right and wrong."). Also, note the line just before the lead section starts:

This article is about the table used in chemistry. For other uses, see Periodic table (disambiguation).

It helps us cover the other cases.--R8R (talk) 00:45, 7 July 2015 (UTC)

"A periodic table is merely a type of table design" - I don't think so. One can not design a table (cols × rows, headers) to be periodic when empty. (The periodicity here only shows when the element's atomic numbers are added - not without them. I.e. when filled, not when designed). Also, "Periodic table" is a long time established common name. So by WP:PRIMARYTOPIC (re WP:disambiguation) this title is considered not ambiguous. Even when IUPAC would use the longer name (I don't bother to check), we can use this short one for being the WP:commonname. Checking the DAB Periodic table (disambiguation) page, I see that there is only one other PT, and that one takes its title by inspiration of this one (as many other, less encyclopedic PT's have). Periodic table of elements correctly redirect to this page. One question: how is it "bothering and confusing" that you arrive on this page while you were looking for it? -DePiep (talk) 07:55, 7 July 2015 (UTC)

I did not mean that I was "bothered and confused" by any difficulty reaching this page. I merely meant that I was bothered by the shortness and apparent informality. I can understand all of the reasons for the title now, thank you. — Preceding unsigned comment added by Zekava (talk • contribs) 18:53, 7 July 2015 (UTC)

Yes, informality is quite allowed in article titles. Or a 'common title', as we say. For example the page is titled simply Bill Clinton. It's OK itf it does not cause misunderstandings. -DePiep (talk) 23:15, 7 July 2015 (UTC)

Moseley

where is Henry Moseley who is actually a real father of periodic table???????? periodicity was discovered not by mendeleev, but by other scientists before him, so I do not understand why he is being mentioned at all??