Wikipedia:Scientific peer review/Francium

Francium

I've recently brought francium up to GA level, and I'd like to take it further. I'm fairly confident about the accuracy and prose. However, I would appreciate input and/or help on expanding it (which is hard, given the utter lack of available information) and refining the technical/style specifics (such as units). Any help would be superb. --Cryptic C62 · Talk 03:18, 30 March 2007 (UTC)

The article is pretty good. One thing that would be interesting to add are more details about how it was discovered (I think it involved co-precipitation with caesium salts, as discussed in the article caesium perchlorate). I would also qualify the statement about it being the "last naturally occurring element to be discovered". More specifically, it was the last element that was originally discovered in nature rather than synthesized from other elements. Other elements that were discovered later, such as astatine, neptunium, and plutonium, were eventually found to occur in nature in trace amounts as well (I'm sure there is a more concise and clear way of phrasing it than mine... ;)

A more general comment is about the reliability of the references. Most are references to a few websites or online periodic tables or encyclopedias. I think the article would stand better to scrutiny with more references to the "hard" scientific literature: journals, review articles, monographs, and advanced textbooks. --Itub 18:48, 2 April 2007 (UTC)

Thanks for the feedback. I'll reread the ChemEducator entry, which focuses on the discovery of francium. As for the sources, you're right. Some of them are not the most scholarly of resources. However, in their defense, most of them include references to hard sources, such as the CRC Handbook of Chemistry and Physics. While I would like to be able to cite those sources, Wikipedia policy (and common sense) dictates that whichever source was actually accessed should be the one referenced. I do plan on going on a library run at some point, so the references should be juiced up by that. --Cryptic C62 · Talk 21:58, 2 April 2007 (UTC)

I just did some copyediting, and what I saw was quite good overall, but I do have three suggestions.

1. Tighten up the lede: it is disproportionately large, and includes some facts that, while cool, need not be mentioned there. This creates obvious redundancies in such a short article. For instance, the employment of Perey, should not, I think, be there, and the "history" section... I'd get it down to at a max 2 paragraphs.
2. Go to the library and read some books! Maybe find the original articles announcing its discovery? You know this, of course, but I feel like emphasizing it here.

Other than that, great article; I shall track its progress closely... -- Rmrfstar 01:58, 3 April 2007 (UTC)

I've truncated the lede somewhat, you may still want the second paragraph to be shaved down. Perhaps tomorrow I will go get some books. --Cryptic C62 · Talk 02:04, 3 April 2007 (UTC)

A quick read made me notice FrF2 in the reactions, shouldn't this be FrF? Or am I missing something here? Also, I agree that a description of the isolation method should be included. There's not a lot on Fr in the literature, but that is one thing that is definitely there and important. Thanks! Walkerma 03:19, 3 April 2007 (UTC)

• I think the discovery bit should be moved into the history section.

• The discovery bit is in the history section...

• Well that was sort of my point - I'm not sure it is worth having this info twice in the article, I just say who discovered it in the intro! -- Quantockgoblin 14:01, 3 April 2007 (UTC)

• Maybe it is just style, but I didn't like (in Applications) "but this idea has since been dismissed" - perhaps better refuted/disproved?

• You're right, "dismissed" is a bit unscientific. I changed it to "but this idea has since been deemed impractical." I think that should suffice.

• Occurrence, nature - I think a reaction scheme here would help like used in Compounds section.

• I see two problems with this. One is that doing this would be redundant. The other is that francium doesn't exist naturally as a compound. As such, reactions and compounds have no place in the natural occurence section.

• Sorry I meant in the Occurrence, synthesis i.e. ¹⁹⁷Au + ¹⁸O → etc ... but no big deal - I just like seeing it laid out. -- Quantockgoblin 14:01, 3 April 2007 (UTC)

• I think there is a little contradiction in the Compounds section ("no compounds or reactions with it have been formed") with discovery section ("with similar chemical properties to caesium"). Maybe no compounds have been isolated would be better? -- just some thoughts Quantockgoblin 10:29, 3 April 2007 (UTC)

• I'm afraid I must be a little harsher than that. If no compounds of francium have been isolated, then the entire "Compounds" section is superfluous: "presumed to have similar chemical properties to caesium" seems to me to be a reasonable application of periodicity. However, it would appear that francium perchlorate has been formed, as it coprecipitates with caesium perchlorate, and several other insoluble francium salts are similarly known (Hyde, E.K., Radiochemical Methods for the Isolation of Element 87 (Francium), J. Am. Chem. Soc., 1952, 74, 4181) The article also quotes a value for the Pauling electronegativity of francium, although the Pauling scale is undefined for elements which do not form covalent compounds. The claim that francium has a lower electronegativity than caesium is widely, though not universally, repeated: this would be expected on the basis of periodicity, but measurements show that the ionization energy of francium is higher (4.0712 eV; Andreev, S.V.; Letokhov, V.S.; Mishin, V.I., Laser resonance photoionization spectroscopy of Rydberg levels in Fr, Phys. Rev. Lett., 1987, 59, 1274) than that of caesium (3.89390 eV; Moore, C.E., Ionization potentials and ionization limits derived from the analyses of optical spectra, Natl. Stand. Ref. Data Ser., (U.S. Natl. Bur. Stand.), 1970, 34, 1). I would like to see a more critical review of the available data, without pretending that we can be exhaustive in our review on WP. Physchim62 (talk) 21:05, 3 April 2007 (UTC)
• There is a further problem with the decay energy of ²²³Fr. The article text claims that Perey observed 45 keV beta particles and that these are the product of francium decay; the infobox gives a beta decay energy for ²²³Fr of 1149 keV... In fact, 45 keV is the energy of beta particles produced by the decay of ²²⁷Ac, as is correctly stated in the infobox for actinium: Perey's equipment was unable to detect beta particles with such a low energy, as is described in the review by Adloff & Kauffman cited in the article, and it is this fact which enabled her to deduce the existence of francium. Physchim62 (talk) 22:38, 3 April 2007 (UTC)

Alright, today I gathered information from hard sources, and I have made a to-do list for myself:

1. Incorporate information from new sources
2. Expand and de-suckify the History section
3. Figure out what's going on with the compounds

I will also use the links that Physchim provided. I appreciate the feedback and support. Please, bear with me for the next couple of days as I try to sift through these materials. --Cryptic C62 · Talk 01:49, 4 April 2007 (UTC)

Okay, I've been looking at this National Nuclear Data thing, and frankly, I just don't want to use it. The half-life chart contradicts almost everything on the CRC chart. CRC is more recent (2006) and I think it's more trustworthy. Unless you can show that the NND list is more accurate than the CRC, I'm switching back to the CRC data. NND = cheesy-looking web page. CRC = 2000 page chemistry encyclopedia. --Cryptic C62 · Talk 02:15, 4 April 2007 (UTC)

One issue which does not seem to have been mentioned yet is the glaring change in formatting. There are two methods of displaying an specific isotope: The "superscript" method: ²²¹Fr and the "longhand" method: Francium-221. The whole article save one section uses the superscript method, and the Isotopes section uses the longhand method. This needs to be changed to a single format for consistancy, probably the superscript method since it appears that that is the predominant method. Other than that, I agree that all of the problems listed above should be fixed as well. --Jayron32|talk|contribs 17:04, 4 April 2007 (UTC)

I've made some significant additions and revisions in an attempt to address your concerns:

• Itub: I've significantly expanded the history section after perusing the Chemical Educator article. I've also added several hard sources, including a few highly-reliable encyclopedia entries.
• Rmrfstar: The lede is somewhat more proportional to the article, and again, I stumbled upon some good sources.
• Physchim62: I rewrote the history section involving decay energies as best I could, though I'm no expert on such technical data.
• Jayron32: I transmogrified all of the superscript isotopes to longhand. I based this decision off of Uranium.

That's not to say that you will all be completely satisfied with the revisions :P. Still to be addressed:

• Quantockgoblin: I'm still not entirely sure of what you're talking about with the discovery bit. Are you saying the sentence in the lede should be removed? Also, I will try to find and list the exact synthesis reactions, as that's a good idea.
• Physchim62: The compounds, of course.

Again, thank you all for your input and support. --Cryptic C62 · Talk 01:15, 5 April 2007 (UTC)

Fix looks good. I didn't have a preference which form you used, as long as it was consistent. Looks fine now. A few more minor points that might need addressing:

• External link in main body of article:Stony Brook Physics... Either wikilink or no link...
• Prior incorrect data: Why is the 1995 estimate of Francium in the article, if the number is wrong? Seems kinda trivial to report that. Why not just give the current, better, estimate and be done at that.

But this article is really improving!--Jayron32|talk|contribs 02:00, 5 April 2007 (UTC)

Fixed both of those. I'm feeling a bit dumb right now. The article Physchim62 pointed out mentions coprecipitation. I have no idea what that is, and I can't find a definition, even here! If someone could tell me what it is, I can work on the compounds section. --Cryptic C62 · Talk 21:58, 5 April 2007 (UTC)

Still looking better. Sorry I keep finding these pickaninny things, but every time something gets fixed, I find something new that needs fixing:

• Encyclopedia Britannica, as good of an encyclopedia as it is, is hardly an authoritative source on isotope data. I would accept CRC Handbook or Merck Index or any of a number of other types of tertiary sources for this type of information, but Britannica... mmm... no. Plus, its not wikilinked, it is externally linked, and again, we shouldn't do external links in the text of an article.
• Expansion of history section: Why was Allison's discovery disputed?

That's all I can find for now.

Bah! Pickaninny. That's what peer review is for, right?

• Alrighty, I wikilinked Britannica. I feel it's valid to keep it because, as you said, it's a fairly relied-upon source of information. That being said, the fact that it lists such a preposterously wrong number of isotopes perfectly demonstrates how the reported number of isotopes varies from source to source. It's meant to be a demonstrative reference, not an authoritative one.
• Somehow I managed to find an article about Allison's device. I only added a sentence to the virginium section, but I think it should be sufficient.

I still don't know what coprecipitation is... :( --Cryptic C62 · Talk 04:39, 8 April 2007 (UTC)

I'm making a fairly major edit to the history section based off a web site and paper I found. As of right now, I'm not done adding the info yet, so don't bother commenting on it *grin*. I do, however, need to find why/how alkalinium was refuted. --Cryptic C62 · Talk 02:48, 9 April 2007 (UTC)

• Regarding the number of isotopes. I wouldn't say the number is not "universally accepted", simply that some references are more up-to-date than others. New nuclides are discovered all the time. I would say that the "true" number is the source that lists the largest number of isotopes (as long as you have no reason to believe that they made some up, or that some of the specific isotopes are truly disputed). This will probably be the most recent source that specializes in nuclear chemistry or related fields. Britannica is not an authoritative source about this, and the discrepancy is not worth mentioning IMO. For all we know, the last time they updated their article on francium thoroughly might have been decades ago!
• Regarding co-precipitation, perhaps google books will help [1] (I haven't read through the results, but there are many, so I hope there's a good one...) Briefly, co-precipitation happens in this case due to the similar sizes of the caesium and francium cations. What happens is that when you have a solution with Cs+, Fr+, and ClO4- and you obtain crystals, they will have a mixed structure (basicaly CsClO4 with some Cs+ sites replaced by Fr+). This is as opposed to a "normal" precipitation, where you would expect more-or-less-pure crystals of the more saturated solute. --Itub 07:10, 10 April 2007 (UTC)

Alright, I removed all references of Britannica, and cut out the section about discrepant isotope reports. So what you're saying about francium is that if it coprecipitates with caesium perchlorate, then it forms francium perchlorate? In other words, francium forms the same salts as other alkali metals, right? --Cryptic C62 · Talk 16:30, 10 April 2007 (UTC)

Sort of, but not really. What coprecipitation means in this context seems to have something to do with separation by differential solubilities. Basically, if you have a solution with a mixture of ions, say for example, Fe²⁺ and Pb²⁺, these cations will exhibit different solubility in the presence of different anions. For example, gradually increasing the concentration of chloride ions (Cl^1-) to the solution will result in the precipitation of PbCl₂ BEFORE FeCl₂, owing to the fact that lead (II) cloride is far less soluble than iron (II) chloride. Thus, you could separate a mixture of the two. There are several factors that owe to the solubility of a salt; however the two biggest in comparing cations are probably ionic radius and valence. Since francium and caesium cations are indentical in both size and valence, they apparently coprecipitate; that is in a solution containing a mixture of them, it is impossible to differentiate between them by precipitation techniques. The same could not be said for, say, sodium and francium, since though they are the same valence (and thus will form ionic compounds with the same formula), their vastly different ionic radius will lead to their salts having different solubilities. I am speculating a lot here, but it is an educated WAG, not a total WAG. Does that sound reasonable?--Jayron32|talk|contribs 16:53, 10 April 2007 (UTC)

As far as I can find, there aren't any lists of francium compounds around. Seeing as this isn't the place for speculation, I'm removing the Compounds section. Given that the only source to even mention francium compounds says that none have been made, I think it's better to just leave it out, at least for now.--Cryptic C62 · Talk 17:18, 10 April 2007 (UTC)

If reliable sources write that they believe francium will act like caesium, you can, I think, include that fact. -- Rmrfstar 21:07, 10 April 2007 (UTC)

The key point about coprecipitation is not the similarity of the solubilities (although they may indeed be similar), but the fact that having similar charge and radius allows a very dilute ion (Fr+ in this case) to be (co)precipitated together with a saturated ion (Cs+), even if Fr+ is way below saturation. I'll give a concrete quantitative example, although the numbers are made up. Let's assume that the solubility products of CsClO4 and FrClO4 are both 0.01 M^2. Imagine you have a solution that is 0.1 M on Cs+. That means that if the concentration of ClO4- gets above 0.1 M, CsClO4 will precipitate (the product 0.1 M x 0.1 M > 0.01 M^2). Now, let's imagine you have a separate solution with a 1 pM (10^-12 M) concentration of Fr+ (not an unreasonable concentration given the rarity and instability of the element). That means that there's practically no way of precipitating the pure FrClO4, because you would need an impossibly high concentration of ClO4- (10^+11 M, according to the ideal calculation!). But now imagine a mixed solution, with 0.1 M Cs+ and 1 pM Fr+. If you increase ClO4- above 0.1 M, CsClO4 will start to precipitate but, since the crystal structure doesn't "recognize" the difference between Cs+ and Fr+ very well, it will carry along some of the Fr+ (i.e., it will coprecipitate). If you manage to precipitate most of the Cs+ out of the solution (by adding a lot of ClO4-, decreasing the temperature, or evaporating the solvent, for example), you will also (co)precipitate most of the Fr+. While you will never get truly pure francium from this method (it will always be mixed with an excess of caesium), it allows you to separate it from other elements that don't coprecipitate with CsClO4 (maybe Ra, Ac, Pa, Pb, etc., I don't know for sure what else was present in the mixture.) Besides the practical use in separating francium from other elements, the fact that it coprecipitated with caesium was part of the evidence that francium was an alkali metal. --Itub 12:36, 11 April 2007 (UTC)

Cool. Your example seems better than mine. That makes a lot more sense. --Jayron32|talk|contribs 17:35, 11 April 2007 (UTC)

If you guys want to add in the coprecipitation information where you see fit, that would be great. I sort of almost understand it, but not well enough to incorporate it into the article. Gahh! And I thought I was good at chemistry. --Cryptic C62 · Talk 00:29, 12 April 2007 (UTC)

I added a short parenthetical note about it to the article. It's probably not worth delving into the topic too deeply in the francium article. One of these days I'll try to create a co-precipitation article... For the time being, there is an interesting quote in the article about Otto Hahn, regarding the importance of co-precipitation for the purification of minute amounts of radioactive elements. I'll paste it here: --Itub 08:39, 12 April 2007 (UTC)

"As a young graduate student at the University of California at Berkeley in the mid-1930s and in connection with our work with plutonium a few years later, I used his book "Applied Radiochemistry" as my bible. This book was based on a series of lectures which Professor Hahn had given at Cornell in 1933; it set forth the "laws" for the co-precipitation of minute quantities of radioactive materials when insoluble substances were precipitated from aqueous solutions. I recall reading and rereading every word in these laws of co-precipitation many times, attempting to derive every possible bit of guidance for our work, and perhaps in my zealousness reading into them more than the master himself had intended. I doubt that I have read sections in any other book more carefully or more frequently than those in Hahn's "Applied Radiochemistry". In fact, I read the entire volume repeatedly and I recall that my chief disappointment with it was its length. It was too short." --Glenn T. Seaborg.

I think the article is really good now. Although I'm not an expert in Francium and I can't vouch for the accuracy of every statement, the article is well-sourced enough so that interested readers can verify the facts if they want. One remaining issue is the electronegativity. I'm pretty sure that it is an extrapolated/estimated value, as thermochemical data is probably not available. However, it is a value found in many sources, so we can include it. If anyone finds a reference specifically discussing the issue of the electronegativity of francium, please add it!. --Itub 08:47, 12 April 2007 (UTC)

Alright, quick update regarding previous concerns:

• There is so little reliable information about francium compounds that it doesn't make sense to make a compound section. Instead, I added the compounds from Hyde's journal entry into the characteristics section.
• Every source I've looked at says the electronegativity value is 0.7, including those given in the element infobox reference page. Only the article Physchim brought up said anything to the contrary. However, I couldn't actually read the article, since it was in a secure database, and the abstract was not much help. From the documents that I can check, the only logical value to report is 0.7.

Those seem to be the only unresolved/unresolvable issues at this point. I'm still scouring databases to find random tidbits (like the surface tension paper). Once I can call that process complete, I may rewrite the lede to better suit the current article. Thence I believe the article is only a few copyedits away from being ready for FAC. --Cryptic C62 · Talk 05:10, 14 April 2007 (UTC)

I found that Pauling uses the 0.7 value in his book The Nature of the Chemical Bond (1960). It doesn't seem to say where it came from, though... --Itub 06:21, 14 April 2007 (UTC)