Wikipedia:Featured article candidates/Heavy metal (chemical element)/archive1

The following is an archived discussion of a featured article nomination. Please do not modify it. Subsequent comments should be made on the article's talk page or in Wikipedia talk:Featured article candidates. No further edits should be made to this page.

The article was archived by Laser brain via FACBot (talk) 14:26, 6 July 2016 [1].

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Heavy metal (chemical element)

Nominator(s): Sandbh (talk) 03:43, 6 June 2016 (UTC)

In 1807 Humphry Davy first discovered metals (potassium, sodium) that floated on water. Scientists of the day debated if these new elements were really metals since all other metals then known were relatively heavy, and sank in water. After some consideration of the other properties of potassium and sodium, they were admitted to the metal club.

A little while later Leopold Gmelin, another chemist, distinguished between light metals and heavy metals on the basis of their density.

Fast forward 199 years to the present day and the term heavy metal seems to have become vernacularised in the language of science even though it has no widely agreed definition. Indeed, an earlier report (2002) described it as an effectively meaningless term.

This article surveys the field of heavy metal definitions including those based on chemical behaviour, sets out the many uses of heavy metals, and summarises their toxicity and their nutritional value.

Smokefoot expressed some amusing and well-intentioned reservations about 2009 and 2015 iterations of this article which prompted me to look much closer at the term and its use in the literature.

John had a pre-FAC hack, and offered some suggestions which I’ve since incorporated. A few other editors, such as YGB; Plantsurfer; and Frietjes, made improvements along the way. Sandbh (talk) 03:43, 6 June 2016 (UTC)

Support by R8R

My comments have been addressed and the article greatly improved during this FAC. I am happy to support the article. --R8R (talk) 10:55, 27 June 2016 (UTC) I'll review the article during this week.--R8R (talk) 17:38, 8 June 2016 (UTC)

A proper review will follow soon, hopefully tomorrow, but is it not worth mentioning in the lead (or at least putting it into a note) that there is a similar term "heavy element", which refers to a different concept (high atomic number, not density)? --R8R (talk) 21:30, 8 June 2016 (UTC)

Done. Yes, this is worthwhile. I added a note in the definitions section to say that, "More generally, any element having a high density, atomic weight or atomic number may be referred to as a heavy element." I had thought that 'heavy element' referred just to elements of high atomic number but, after looking around, I see that it can also be applied to elements of high density or atomic weight. Sandbh (talk) 00:31, 10 June 2016 (UTC)

Overall, this is a good article. A few comments:

• A general comment that comes to my mind (please correct me if I'm missing something) is that, rather having a single undisputed definition, the term has multiple definitons depending on context, and this would be great to underline in the text. It makes little sense to talk about "heavy metals" as of dense metals in the contexts of nuclear reactions, as densities don't make the most important thing in this context, as it makes little sense to underline high atomic number in a context of, say, producing new alloys. (Lead, for example, is a heavy metal in the context of atomic numbers as well as in the context of densities.) This could possibly interfere with the small para on the term "superheavy metals."

• I also note this should be underlined in the lead section. Right now, it only defines "heavy metals" as quite dense metals, and says there are some other meanings (no clue in how they differ from the first definition). See, for example, the lead section from the Polish article (as translated by Google Translate):

Heavy metals - imprecise term for variously defined set of metals and semi- characterized by high density, often toxic properties. In various publications can meet differing significantly limits the density above which the element is considered to be a heavy metal: 3.5, 4, 4.5, 5, 6 and 7 g / cm³. There are also a number of definitions based on atomic number - eg. Metals and semi-metals having an atomic number greater than 11 ( sodium ) or 20 ( calcium ), or mass number . There are also selected based on the definitions of chemical properties, such as. The number of acceptor ( acidity Lewis ) and definitions made ​​based on a range of applications including, for example. Usefulness in the manufacture of ammunition arms or conduit retaining ionizing radiation [1] .

Perhaps one way to start the article mentioning the possible definitions without going into detail reserved for the corresponding section would be "Heavy metal is a term that depending on context may specify metals of great density, great atomic number/atomic mass, or specific chemical behavior (see [[#Definitons]] below), referring to metals and sometimes some metalloids."--R8R (talk) 13:13, 10 June 2016 (UTC)

Done. I changed the lede so that it also mentions definitions based on atomic number atomic weight, and chemical behaviour. I appreciated your question; I had to think at length about it. Sandbh (talk) 12:16, 13 June 2016 (UTC)

I think the current lead certainly does a better job at introducing a reader into the term. However, I am still a little concerned with density being such a defining property. For example, the newly added information on radioisotope synthesis shows one aspect where density plays no defining role, as lead, bismuth, thorium, and uranium aren't chosen because they are dense even though they are dense; they are chosen because their atomic numbers are high. And as such I don't think it is necessary to start off with mentioning density as concept-defining even though this must've been the case historically.--R8R (talk) 11:51, 16 June 2016 (UTC)

Done. I amended the lede to make mention of differing contexts, and I added examples of these differing contexts in the first paragraph of the definitions section. I think (hope) it's looking good now. Sandbh (talk) 02:00, 17 June 2016 (UTC)

It is, and I'll strike the initial comment, but as a side note, one of the sources (Hawkes 1997) says the author was first introduced into the term as defined by (apparently) chemistry, and this might also have to be be listed among possibilities in the first sentence.--R8R (talk) 08:23, 17 June 2016 (UTC)

Done. The opening sentence of the lede now makes mention of some of their chemistry. Sandbh (talk) 09:57, 18 June 2016 (UTC)

• (minor) I can't help but notice that densities of the heaviest elements have not yet been measured, so the colored table must have a note on that. Or note the approach the German Wiki uses.

Done. Note added to table title. Sandbh (talk) 12:45, 11 June 2016 (UTC)

The German Wiki has also given me the idea to address the red sea in the middle of the table, by splitting it into amber (10–19.99) and red (≥20) like they do (notice how they bold Re, Os, Ir, Pt, and Np)! Double sharp (talk) 16:42, 18 June 2016 (UTC)

The amber is pretty! Sandbh (talk) 03:56, 19 June 2016 (UTC)

• Since the Etymology section could be named History, I think it would be great to briefly mention the emerging of the term "heavy metal"/"heavy element" in a context of nuclear reactions.

Done. Sandbh (talk) 2:29 pm, Today (UTC+3)

• (very minor) "Magee notes that the actinides were once thought to represent..." On reading this, I stopped for a second and thought if this Magee had even been mentioned. I learned that this is indeed the first place where a reader meets this name. I think a little trouble could be saved by moving the reference to after the name, i.e. "Magee[50] notes that the actinides were once thought to represent..."--R8R (talk) 11:51, 16 June 2016 (UTC)

Done. Sandbh (talk) 14:01, 16 June 2016 (UTC)

More to come later.--R8R (talk) 08:51, 9 June 2016 (UTC)

I can't really judge the Uses sections without looking too closely, which I must be unable to do for now, but could you explain the general principle on which the uses to be mentioned were selected? For example, it doesn't mention two of the three uses that came to my mind: tungsten wire in light bulbs, lead--acid batteries (batteries have only been mentioned in one word, while this is the largest use of lead), and lead bullets (which are mentioned). There may be a good rationale behind this, but I'd like to know it. (I'd want to add that I can't immediately think of a good way to choose which uses are important enough to be mentioned and which aren't.)--R8R (talk) 18:29, 12 June 2016 (UTC)

Done. I reorganised and supplemented the uses section so that it now refers to general uses, density-based uses, (high) atomic number reliant uses, and other uses. I'm not aware of any atomic weight based uses. I haven't said anything about W in light bulbs because this use, as I understand it, is based on the high melting point of W rather than something more specifically associated with it being a heavy metal. Same principle applies to Pb in batteries. Sandbh (talk) 12:16, 13 June 2016 (UTC)

This explains a lot and the section looks great after the reorganization.--R8R (talk) 11:51, 16 June 2016 (UTC)

Before I continue the review, I would love to support further great improvements the article is undergoing during the FAC.--R8R (talk) 11:51, 16 June 2016 (UTC)

Welcome onboard :) Sandbh (talk) 02:03, 17 June 2016 (UTC)

I'll skip the Toxicity section for a while and comment on Biological role. Both sections seem a bit too short. Of course, this can't be an issue to ask to address without specifying what, if anything, is missing, and unfortunately, toxicity and biology are not fields I am an expert at. However, regarding the Bio section, I would like to propose, similarly to what has been done for the Uses section, a general story that focuses not only on what elements do, but also on the correlation with the term "heavy metal". So I suggest the section start like this: "Heavy metals don't have basic functions in living organisms, but some period 4 metals are trace essential elements, with iron used for hemoglobin in blood, zinc for X, Y for A, Z for B, etc. Heavier metals are rarely important for living organisms: of all period 5 elements, molybdenum is essential for humans [and I don't know if any other period 5 elements are used by organisms for anything]. In period 6, only tungsten is used by some bacteria and not eucariots, and the only metal used in biology heavier than tungsten is uranium also used by some bacteria." Maybe it would be great to say they are not so important in organisms because they are rare in nature (if this can be referenced). This, by the way, brings me into the question if we should have a section on occurrence and formation of these elements (which I think would be nice to have).--R8R (talk) 13:50, 17 June 2016 (UTC)

Double sharp has pointed me to the fact uranium is not necessary for those bacteria, although beneficial; it would be great to point out there are metals that have this property (DS hints the same is true for tantalum in human body).--R8R (talk) 16:23, 18 June 2016 (UTC)

Yes, Ta is biocompatible and for that reason gets used in implants. But generally Ti is used instead for cost purposes. Most of the refractory metals work (in particular, Ti, Hf, Nb, Ta, Re). Note that these are the pure metals; as ions, some (Nb) are more toxic than others (Re, which from limited animal studies appears to be about as harmful as table salt – i.e. not very). Double sharp (talk) 16:40, 18 June 2016 (UTC)

I've edited and augmented the Bio section, so it now surveys the period 4, 5 and 6 elements, as well as the ones that are not essential but have beneficial effects anyway. We can discuss further but I see no value in referring to the period 4 elements in this section as something other than heavy metals---they meet the criteria and even the literature refers to them as essential heavy metals. I'll see if I can find something about the heavier ones not being so important, due to their rarity. On a Formation and Occurrence section, I presume you're talking about nucleosynthesis, the iron peak, and whether they are lithophiles or chalcophiles etc? Sandbh (talk) 10:33, 19 June 2016 (UTC)

I did not mean to imply it should somehow be noted that period 4 elements are not heavy metals or something---perhaps wrong wording on my side. Re Formation and Occurrence: yes, exactly.--R8R (talk) 11:24, 19 June 2016 (UTC)

Thanks. BTW I found a reference on the link between essentiality and abundance, and have weaved that into the paragraph as an intro to the heavier heavy metals. Sandbh (talk) 13:37, 19 June 2016 (UTC)

Since Toxicity and Biological role have been merged (which generally makes sense), I'll look at what's been done closely when reviewing the part on toxicity.--R8R (talk) 09:00, 20 June 2016 (UTC)

I have carefully read the resulting section and I see no major issue with it. There is a minor one, however: I think it's illogical to have information on positive effects of heavy metals to be both preceded and superseded by the information on negative effects; I think the latter should be put in the beginning of the section?--R8R (talk) 15:31, 22 June 2016 (UTC)

That was good feedback. I've split the Toxicology and biological role section back into two sections (which is the way I always preferred it) and made some other adjustments. I think the flow should be OK now. Sandbh (talk) 03:28, 23 June 2016 (UTC)

Indeed, I'll strike the initial comment--R8R (talk) 09:00, 23 June 2016 (UTC)

At this point, my review is finished, and I am waiting only for the issue just above to be resolved or explained and for a new section on formation and occurrence. The article has undergone great changes and I'll be happy to support it once these are resolved.--R8R (talk) 15:31, 22 June 2016 (UTC)

A new section on formation, occurrence and abundance has been added. Sandbh (talk) 13:50, 25 June 2016 (UTC)

Well done. Just two notes:

"Rather, they are largely synthesised by neutron capture." -- I think it would be great to briefly mention the difference between the s- and p-processes, mainly because you later explain what happens in the s-process.

I added a note to the end of the neutron capture paragraph, giving examples of p-process drivers. Since the focus of the paragraph is on the major production route for the post- iron peak elements, and p-processes are minor players I think a note will be appropriate in this case. Sandbh (talk) 10:01, 27 June 2016 (UTC)

A typo on my side: I meant the s- and r-processes. Anyway, I just added a little info on that (tried to add not too much to not go off the topic); reorganize that in any way if you want.--R8R (talk) 10:53, 27 June 2016 (UTC)

"Stars lose most of their mass when this is ejected late" -- this caught my eye while I was reading it. What's "this"? Oh, I got it; come to think of that, it was clear enough, but I put "it" instead.--R8R (talk) 15:28, 25 June 2016 (UTC))

--R8R (talk) 15:25, 25 June 2016 (UTC)

Additional comments

(these comments will not affect my readiness to support the upcoming promotion, as the following is not something explicitly stated in the FA criteria; still, they are worth addressing)

• The red used in both tables makes symbols to difficult to read. Easy solution: replace it with #FFAAAA. An explanation would include the fact the color for wikilinks is #0645AD, and color contrast between the background and text should be greater than or equal to 4.5 to follow the standards (this, by the way, does make the text easier to read).

  I changed the color a bit; do they look better?--R8R (talk) 03:07, 26 June 2016 (UTC)

• I think the most outstanding metal in the occurrence table shouldn't have the least distinguishable color.--R8R (talk) 15:25, 25 June 2016 (UTC)

The new colours are fine. Are you wanting the background colour of Fe to stand out more? I'm not happy about the width of the abundance table, and am not sure why it is wider given it's based on coding used in the density table but I presume this is a minor point that can be worked on in the background. Sandbh (talk) 03:27, 26 June 2016 (UTC)

Yes, that's what I meant. (Also, it would make sense to me if the most abundant metals were red and orange going to green and blue, but I won't insist. Again, color picking is not a part of the FA criteria and this is an FAC, after all.) My first thought was that it was because the table had to fit in all the labels: I've changed the font size and, as expected, the table became smaller; is this what you wanted?--R8R (talk) 03:48, 26 June 2016 (UTC)

Fe looks like a beacon now, which is good. The colours are that way so that the less abundant heavy metals have the more alarming colours. There's a little bit of literature on this re shortages of strategic metals. Does that make sense? The table width is better, thank you. I hadn't thought about changing the font size. I thought it had something to do with the column widths not behaving whereas they do behave as expected in the density table. Sandbh (talk) 04:54, 26 June 2016 (UTC)

Glad to know I helped. Re red--blue transition: oh yeah, reasonable enough. I took a closer look at the table, and the solution turned out to be poor (working, but not being nice): both tables now had equal widths but different font sizes. I spent almost an hour trying to find a good solution, and the solution was to simply break the title of the second table into two lines.--R8R (talk) 05:28, 26 June 2016 (UTC)

Pretty colours! Double sharp (talk) 06:09, 26 June 2016 (UTC)

And I adjusted the table heading some more so that it's nicely spaced and centred. Thank you for your well spent-hour. Who would've thought it was the stupid title, even though the row spanned all 20 columns. More later---have go and walk the dog. Sandbh (talk) 06:45, 26 June 2016 (UTC)

Double sharp: thanks for your compliment. I basically applied what I learned from DePiep when constructing my first version of recolored PT: all colors should have same saturation and value in the HSV color space. To pick them, I sought for a shade of read distant enough from wikilink color to pass the distunguishability test and constructed other colors with same S and V (they all pass the test as well).

Sandbh: thanks for your appreciation. I was surprised as well, I tried that when I couldn't find any reason why the tables were different even with a text analyzer. Who could've thought.--R8R (talk) 10:53, 27 June 2016 (UTC)

Image review

• File:Lead_shielding.jpg: can you fix the auto-generated source?

Done. Sandbh (talk) 09:53, 14 June 2016 (UTC)

• File:Laser_glass_slab.jpg: if you follow the "site policies" link from the current licensing tag, you'll find that "they consider their work potentially copyrighted" - can we clarify this status? Nikkimaria (talk) 22:25, 10 June 2016 (UTC)

OK, thanks. The site policies page says that Lawrence Berkeley National Laboratory '("allows "non-commercial, educational, or scientific use," but other work potentially copyrighted)'. I presume our proposed use would fall within the non-commercial etc policy. Is this acceptable? Sandbh (talk) 09:48, 14 June 2016 (UTC)

No - Wikipedia does not allow non-commercial or "educational use only" licenses, except as fair use. Nikkimaria (talk) 12:07, 14 June 2016 (UTC)

Right then. I've changed the image. How does it look now? Sandbh (talk) 12:38, 20 June 2016 (UTC)

Hi @Nikkimaria: Could you have please review the new image for compliance? Thank you, Sandbh (talk) 13:50, 25 June 2016 (UTC)

Yes, it looks fine, thanks. Nikkimaria (talk) 15:22, 25 June 2016 (UTC)

N

Oppose I am sorry, but I seriously think this article does not cover the subject matter very well. I have yet to see anybody call vanadium a heavy metal, and the article spends more time talking about vanadium and chromium than say lead, gold, mercury. No serious chemist in their right mind would call iron or zinc heavy metals. Most times I've heard the term heavy metal has been in reference to environmental and toxicity aspects so I suggest expanding a bit on that. I seriously recommend restructuring the article to focus on period 5 and 6 and try to only mention casually definitions including anything in period 4 since pretty much almost all elements up to zinc are used in biology. Nergaal (talk) 06:28, 13 June 2016 (UTC)

Nergaal, this is good feedback.

To address your concerns I:

• adjusted the lede so that toxicity was mentioned earlier on, and added some words about environmental concerns
• moved the toxicity section (and the accompanying nutrition biological role section) higher up in the article and added a paragraph on the environmental aspects of heavy metals
• added a paragraph, in the definitions section, mentioning the disputed status of some of the period 4 d-block metals as heavy metals (i.e. Sc, Ti, V, Cr, Fe, Cu, Zn).

Counting individual mentions of elements, those in periods 5+ are now mentioned nearly twice as often as those in period 4.

In light of all of the above, could you please reconsider your Oppose? Sandbh (talk) 11:29, 16 June 2016 (UTC)

DOn't get me wrong, the article is nice but I do find it misleading. It is slightly better yet it is still tilted towards 1st row. Maybe outside my field people actually use this term loosely, but AFAIK, all (maybe except chromium) metals in 1st row plus Mo and W are used in biology in various enzymes. So to a certain degree I think it is unlikely that these elements are "toxic heavy metals". On the other hand, exactly because all the other are not used in any roles in the cell, they are likely toxic. I would like to see a quote saying Mn Co and Ni are heavy metals. I suggest focusing even more on the non-1st row with something like "while 1st row has been mentioned as HM, pretty much everybody agrees that elements after X are heavy metals. For examepl, y is bad, z is really bad, zz is deadly, etc." Currently definitions and etymology feel like they overlap quite a bit. Also, most references need cleaning up since they have no "." after initials. Nergaal (talk) 15:22, 16 June 2016 (UTC)

Thank you.

1st row metals

I think you are right. All the metals from V to Zn (Mo and W) appear to be used in biology. With the exception of hexavalent Cr, I wouldn't think of any of them as being particularly toxic (except if I was exposed to some of their fumes or carbonyls). Looking at the metal toxicity article, I can see entries for Cu, Fe, Mn and Zn poisoning; and Emsley, in Nature’s building blocks, talks about mining or industrial hazards attributed to Ti and Ni. So I can see that these metals are toxic in some situations, as well as being essential nutrients in trace amounts.

Anyway I found a better reference challenging the status of all the metals from V to Zn as heavy metals, and I found another reference disputing the status of e.g. In, Rh and Os as heavies, on the grounds that they're too rarely encountered as environmental hazards. So I updated the paragraph about all of this in the Definitions section, to give it more diverse perspective.

I presume that since Mn, Co and Ni are now picked up as metals whose status as heavy metals has been challenged, it won't be necessary to include a citation that mentions them as heavy metals? They're picked by any of the density-based definitions, and by Hawkes' periodic table location definition.

I’ll have a closer look at your suggestion about y is bad, z is really bad. It may not be feasible. The only possibly bad non-1st row transition metal that comes to mind is Os. I suspect that none of the others are particularly "bad" except for the ones that are mined a lot and I'm guessing there are not many of these among the heavier transition metals (whereas a lot of the 1st-row metals are mined a lot/used by industry).

I reviewed the toxicity of the transition metals; the period 4+ post-transition metals and metalloids; the Ln; and the An up to U. Here are the results (elements not listed have no more than low/mild/moderate toxicity):

Period 4

Sc...some of its compounds (it has been suggested) are carcinogenic

Cr…can be toxic in excess; hexavalent form is carcinogenic

Mn…dust/fumes damage the central nervous system; permanganate ion is toxic

Fe…> 5 gm in soluble form causes liver and kidney damage and can be lethal

Co…a large dose could be life threatening; suspected carcinogen

Ni…associated with mining and industrial hazards; dust is carcinogenic; carbonyl is lethal

Cu…can be toxic in excess; 1 gm of copper sulphate can be fatal; survivors have suffered major organ damage

Zn…can be toxic in excess

As…bad

Se…> 5 mg is highly toxic

Period 5

Mo…highly toxic in larger doses

Ru…little threat; RuO₄ is toxic

Pd…could be toxic in higher doses

Ag...extremely toxic to aquatic plants and animals

Cd…bad

In…toxic if more than a few mg are consumed

Sn…organometallic compounds are toxic

Sb…can kill

Te…2 gm of sodium tellurate can be lethal

Period 6

Os…little threat; OsO₄ is toxic

Hg…bad

Tl…bad

Pb…bad

Bi…damages liver if taken in excess

An…radiation aside, U is poisonous

On this basis I don’t see a need for changing much. Sandbh (talk) 06:08, 19 June 2016 (UTC)

I've expanded the toxicity section and merged it with the biological role section, so that the whole section now talks about the more toxic HMs, then the essential HMs but with the potential for toxicity; and lastly the non-essential ones. Sandbh (talk) 10:28, 20 June 2016 (UTC)

Overlap: Definitions and etymology

The two sections look at the topic from different perspectives. The Definitions section covers the present situation; the Etymology and usage section traces the chronology of the term and its usage over time. At the expense of some overlap, I think its preferable to keep the two perspectives separate for the benefit of the reader who may not be that interested in the historical details.

Tilt towards 1st row?

I rechecked mentions of named first row transition metals, and other heavy metals (not counting the Notes). Going by section, the count is Lede (0/0); Definitions (0/4) [excl. the challenge para.]; Etymology (2/1); Toxicology (5/11); Biological roles (7/1); Uses (20/42)—Overall (34/59). This appears to be a reasonable distribution. In the Biological roles section, the 7:1 tilt in favour of the first row transition metals is due to the fact that these metals happen to be ones with nutritional roles.

References: "." after initials

I’ve been following the referencing guide from my alma mater, which doesn't use " . " after author initials. Is there a MOS requirement for this? (if there is I could nae find it) Sandbh (talk) 12:39, 18 June 2016 (UTC)

• The class A/B donors is something I haven't heard and is not wikilinked. Are your referring to hard/soft donors? Nergaal (talk) 19:42, 18 June 2016 (UTC)

Sort of. The hard/soft terminology, as I understand it, comes from Pearson (1963, 1968, 1969). His work is based on Ahrland et al. (1958) who introduced the class A/B/borderline categories. Nieboer and Richardson (1980) took the hard/soft concept, which they said was restricted to inorganic systems, and applied it to biological systems. Sandbh (talk) 14:27, 19 June 2016 (UTC)

• I'll reply alter, but could you find a way to emphasize the elements that everybody agrees are heavy? For example metalloid has a clear group of commonly recognized ones. Nergaal (talk) 19:50, 18 June 2016 (UTC)

I amended the lede to make mention of Cd, Hg and Pb as examples of heavy metals that are toxic. I guess these are the three most well known heavy metals in that context. I left out As given it seems to have some kind of biological role, and it's commonly regarded as a metalloid. Sandbh (talk) 04:41, 22 June 2016 (UTC)

• The element articles are not particularly good sources. Just check out IDLH and see how many elements not listed by you are there. The reason people don't tend to discuss some of the heavier elements is because they are not commonly encountered in everyday applications, not because they are not toxic. Even W is listed if you seach here. Nergaal (talk) 18:07, 26 June 2016 (UTC)

Thanks Nergaal I appreciate your thoughts. I was guided by Emsley's assessment of the toxicity of the period 4–6 HMs, supplemented by the other seven references cited in the toxicity section. (W is mentioned in the note at the end of the first paragraph of this section). Metals I haven't mentioned apparently have relatively low/mild/moderate toxicity. For example, going by IDLH and Emsley, V₂O₅ causes local respiratory effects after a few hours of exposure; Zr compounds "possess a low order of toxicity"; Pt may cause an allergic reaction in some sensitised individuals in which they experience symptoms similar to asthma or a cold.

Of course, any substance will be toxic if administered in a sufficiently large dose. My objective in this article was to present a global view of heavy metals rather than concentrating on any particular aspect, such as toxicity. For that reason I've attempted to focus the toxicity discussion on the more notably toxic heavy metals, rather than every heavy metal (which is something I suggest would be the purview of an article such as metal toxicity).

In any event I checked for entries in the IDIL index for the other HMs not mentioned in the toxicity section: Sc, Ti, Ga, Ge; Y, Nb, Mo, Tc, Pd; La/Lu, Hf, Ta, Re, Ir, Au, Po and At. Either there was no entry or the entry appeared to be benign. Sandbh (talk) 09:15, 29 June 2016 (UTC)

@Nergaal: I'll cross check the toxicity section against Casarett & Doull's Toxicology: The Basic Science of Poisons, which seems to be the gold standard. Sandbh (talk) 02:45, 30 June 2016 (UTC)

Cassarett & Doull's chapter on the toxic effects of metals addresses the following HMs:

Period 4: V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se

Period 5: Mo, Pd, Ag, Cd, In, Sn, Sb, Te

Period 6/7: Pt, Au, Hg, Tl, Pb, Bi, U

Having checked this chapter I've added V, Ge and Pt to the toxicity section. How does it look now? Sandbh (talk) 11:48, 30 June 2016 (UTC)

• Just noticed the occurrence section. Why aren't the two PT images containing the same highlighted elements? And what are the lines/boxes supposed to represent? Nergaal (talk) 03:42, 30 June 2016 (UTC)

There is a large discrepancy in the second table and the Goldschmidt classification one. Nergaal (talk) 03:44, 30 June 2016 (UTC)

The first table shows the density of all the elements, including the artificial ones; the second table shows the abundance and primary geochemical classification of the naturally occurring elements in the Earth's crust (thanks to User:Double sharp for help with the second table; also there is a note at the end of the Least abundant legend saying that elements having abundances a lot less than the 1 part per trillion of Ra and Pa are not shown). The dividing line divides the lithophiles from the chalcophiles. The boxes around Au and Sn show that although these two elements lie on the chalcophile side of the table they actually occur as, respectively, a siderophile and a lithophile. This is mentioned in parentheses after where it says "chalcophiles". The Goldschmidt periodic table shows the geochemical classification of the elements in the whole of the Earth, rather than just the crust, hence the difference. Does this help? Sandbh (talk) 05:08, 30 June 2016 (UTC)

@Nergaal: Did you have any other concerns? Sandbh (talk) 08:30, 4 July 2016 (UTC)

• Oppose At this point the references are very poorly formatted. Initials on names are missing "."s. There are very few links to any online content for references. Surly there are some google books and web sites that will be usable. There are also very few wikilinks for authors, or publishers. There are other minor problems such as ref "Close F" with date: 12015. Some references are quite old, and should be replaceable by newer ones. Also the Neodymium sulfate picture has no alt text. Graeme Bartlett (talk) 12:52, 27 June 2016 (UTC)

Thank you Graeme.

I’ve been following the referencing guide from my alma mater, which doesn't use " . " after author initials. Is there a MOS requirement for this? (If there is I couldn't find it.)

There are 15 links to online references, including Duffus' IUPAC paper, Hawkes' discourse on what is a heavy metal, and Habashi's paper on Gmelin's 1817 Handbuch, in which the latter appears to have first distinguished between light and heavy metals on the basis of density. I don't link to Google books since, in my experience, Google periodically changes the results the views it offers for any particular book. In the past I've saved Google books links in other topic areas only to find that when I wanted to go back and recheck the search result I can no longer access that particular view. If I find relevant and reliable web pages I'll link to them however I find that the bar for reliability eliminates the sizeable majority of them.

Wikilinks for authors and publishers is not something I knew was an FAC requirement. It wasn't for the last FAC article I worked on in April 2015 (Astatine) and I see there were no publisher wikilinks on yesterday's FA article, Robert of Jumièges (nor Google books links). Are wikilinks for authors and publishers an FAC requirement?

I've rechecked and corrected the formatting of the references.

The older references appear to largely deal with descriptive chemistry. This kind of chemistry writing largely dried up from about the 1950s onwards, or has been forgotten. As I understand it, age doesn't disqualify older works; they still have value. I remember looking for more recent references in some cases however later references tend to deal more with principles and gloss over descriptive nuances. If there are any particular references you think need to be updated I'd be happy to review these.

The neodymium sulfate image now has an alt tag. Sandbh (talk) 02:42, 30 June 2016 (UTC)

I can see many edits to improve what I complained about. So I may have to change my mind. Graeme Bartlett (talk) 07:02, 30 June 2016 (UTC)

I will add some more small issues.

Thank you Graeme, I appreciate your proof-reading-fu. Sandbh (talk) 14:07, 1 July 2016 (UTC)

• in "Densities of metals and metalloids in the periodic table" there is some strange characters around "I", probably to center it, but K and F do not have this.
• In this same table C appears as "C|"
• ref: Rainbow PS 1991, "The biology of heavy metals in the sea", in J Rose (ed.), Water and the environment, Gordon and Breach Science Publishers, Philadelphia, has a bad kind of dash in page range 415‒432
• Author of "Gunshot wounds: Practical aspects of firearms, ballistics, and forensic techniques," (DiMaio) appears on actual book cover as Di Maio (half fixed)

Fixed

• In note 9, I think it is a bit undue talking about Astatine hydroxides and sulfides. I do not think that Astatine, or other substances too radioactive to form a liquid or solid would be classed as heavy metals! Also the Duck J. Yang, William L. Jolly, Anthony. O'Keefe reference caused me to laugh, due to the Duck and Jolly, but perhaps this is serious!

I understand your concern about At. Condensed At has been predicted to be a metal; with sufficient cooling, it has been suggested that it may be possible to observe condensed At. For those reasons I thought it was worth including.

Yes, very occasionally I see author names that are interesting. There are two references in the list by the same two authors, for different volumes of the same work. Luckey & Venugopal, and then Venugopal & Luckey. That cause me a double-take but it turned out to be right. Sandbh (talk) 14:21, 1 July 2016 (UTC)

• density units should be standardised. we have gm/cm.3 gm/cm3 and g/cm3 (should be g/cm³) (I fixed another two, density is important for heavy metals!)

Fixed

• jewellery or jewellery?

The first version is preferred; the second version appears because that is how it was recorded in the journal article title

• Macmillan or MacMillan?
• Advanced Motorsport Engineering uses capital letters in its title. (Actually most titles in the list are incorrectly capitalised) The alma mater referencing guide needs to be ignored and the best practice on Wikipedia needs to be used. This is supposed to be the "best work", not something that is just good enough to pass criteria.

Clarification requested: I couldn't see any caps in the title in question, nor caps in most of the titles in the list (aside from journals). I have, however, added periods after author names.

The periods are good. My issue is with book titles, which should use title case. Journal titles can use title case or lower case. I am happy to change this, but first I like to see us all trying to achieve the same thing. Graeme Bartlett (talk) 08:44, 2 July 2016 (UTC)

Ah, the penny dropped, after I posted my comment. Please go ahead and change the book titles to title case and thank you for the offer. Sandbh (talk) 00:13, 2 July 2016 (UTC)

I have title cased the books now. Graeme Bartlett (talk) 08:44, 2 July 2016 (UTC)

• Structure-property or Structure–property

Fixed

This does not look to be changed, but since one is in a reference title and one is in a quote, I will say it is not a problem.

Graeme Bartlett (talk) 08:23, 1 July 2016 (UTC)

Has now been fixed, properly. Had an iPad moment when I mangled the edit summary. Sandbh (talk) 11:49, 2 July 2016 (UTC)

stiking some fixed issues. Graeme Bartlett (talk) 13:11, 1 July 2016 (UTC)

• Is it possible to merge the "citations" and "references" sections as much as possible? They really only need to be distinct where there are more than one reference to different parts of the same work. It would be useful if there were many different pages from just a few books used for the whole article. As it stands it makes navigation to the actual reference extra complex, and for most of these there would be only one use any way. Graeme Bartlett (talk) 02:28, 7 July 2016 (UTC)
• I will also investigate whether there are DOIs for some of those journals, and whether authors have article here on Wikipedia or not.

Coordinator note: Substantial issues have been identified here that should be worked on outside of the FAC process. Therefore, I will be archiving the nomination. --Laser brain (talk) 14:26, 6 July 2016 (UTC)

• Closing note: This candidate has been archived, but there may be a delay in bot processing of the close. Please see WP:FAC/ar, and leave the {{featured article candidates}} template in place on the talk page until the bot goes through. --Laser brain (talk) 14:26, 6 July 2016 (UTC)

The above discussion is preserved as an archive. Please do not modify it. No further edits should be made to this page.