Talk:Abundance of the chemical elements/Archive 1

Argon
I'm debating the phrasing I use with regard to argon in the bottom. I know they get helium out of natural gas wells, and it would surprise me if argon isn't found in the crust at all; I know it's generally produced by distillation of liquid air, so I doubt it's a major component of the crust (since it'd be cheaper to get it there if it were), but I wonder if that's an error in the original page. Argon must occur between the grains of sandstone in greater abundance than some elements that are listed -- Pakaran 13:18, 8 Dec 2003 (UTC)

On another note, if anyone wants to make a list for the universe, see, which is the best source I could find. I get the following log10 figures for their numbers, keeping 3 digits, which is more than they do:

COMMENT: The abundance of hydrogen in the earth is incorrect since it should be vastly more than oxygen. I do not know a source for the information H is combined in various forms, as is oxygen, but the abundance does not refer to free hydrogen gas but to the atomic species.Drpco2 (talk) 05:19, 2 March 2014 (UTC)
 * H 4.08
 * He 3.45
 * O 1.20
 * N .90
 * C .48
 * Fe .42
 * Si 0 exact
 * Mg -.051
 * S -.481
 * Ni -.678
 * Al -1.05
 * Ca -1.15
 * Na -1.34
 * Cl -1.60

Pakaran 13:30, 8 Dec 2003 (UTC)


 * The standard abundance distribution used for the Sun in the astrophysics community is derived from one by Anders & Grevesse, Geochimica et Cosmochimica Acta (ISSN 0016-7037), vol. 53, Jan. 1989, p. 197-214. There have been several improvements (some minor, some important) to that distribution since 1989. Those are normally on an element-by-element basis, which are published in normal refereed journals. However, new comprehensive tables for all elements -- which is what I'd like to insert into Wikipedia -- tend to get published only in conference proceedings and are difficult to find.  This standard abundance distribution is derived from both lab analysis of primitive meteorites and spectroscopic analysis of the Sun. BSVulturis 19:32, 15 December 2006 (UTC)

Could someone add some consideration on the abundance of elements on plants, animals ans specially the human body? Or, if you think here is not the place, add a link to the proper article?

Rend 01:47, 10 August 2005 (UTC)

Human Composition
I've found about the human body, I don't know how up to date the source, sorry, I can't update right now, im in a hurry, could someone add this for me?

Most of the human body is made up of water, H2O, with cells consisting of 65-90% water by weight. Therefore, it isn't surprising that most of a human body's mass is oxygen. Carbon, the basic unit for organic molecules, comes in second. 99% of the mass of the human body is made up of just six elements: oxygen, carbon, hydrogen, nitrogen, calcium, and phosphorus.


 * Oxygen (65%)
 * Carbon (18%)
 * Hydrogen (10%)
 * Nitrogen (3%)
 * Calcium (1.5%)
 * Phosphorus (1.0%)
 * Potassium (0.35%)
 * Sulfur (0.25%)
 * Sodium (0.15%)
 * Magnesium (0.05%)
 * Copper, Zinc, Selenium, Molybdenum, Fluorine, Chlorine, Iodine, Manganese, Cobalt, Iron (0.70%)
 * Lithium, Strontium, Aluminum, Silicon, Lead, Vanadium, Arsenic, Bromine (trace amounts)

Found at: http://chemistry.about.com/cs/howthingswork/f/blbodyelements.htm

Reference: H. A. Harper, V. W. Rodwell, P. A. Mayes, Review of Physiological Chemistry, 16th ed., Lange Medical Publications, Los Altos, California 1977.

Rend 03:07, 13 September 2005 (UTC)

I'm having a little trouble with this list. I have to assume these chemists know more than I do, but simple logic makes me wonder how hydrogen can be 10% of the body? If most of the body is water (65 to 90%) and water is made up of two hydrogen atoms and one oxygen atom, how can there be more oxygen (65%) than hydrogen (10%) in the body? Something's not adding up.

Hillsc 04:49, 9 September 2006 (UTC)

The list is by mass. Oxygen atoms are sixteen times as massive as hydrogen atoms.--Syd Henderson 01:22, 16 September 2006 (UTC)

But how many elements?
This article discusses relative abundance, but not absolute abundance. How many *naturally occurring* elements are on the earth? In the universe? What are their names?

Norm

Naturally now present on Earth are all the stable elements, plus those with isotopes with half-lives of roughly a billion years or more, plus some small amounts of the unstable decay products of those. That means all the elements up lead (excepting the pure-unstable elements Tc and Pm), plus Th and U (which are unstable but with billion-year half-lives), and finally plus tiny proportions of the elements between Pb and U (the decay products of U and Th). Human activity in the Atomic Age has added traces of others. BSVulturis 19:13, 15 December 2006 (UTC)

As for which these are on the periodic table, they are all elements with numbers less than that of uranium.--Scorpion451 01:16, 13 July 2007 (UTC)
 * The first two transuranium elements, Np and Pu, are naturally produced by neutron capture in natural uranium ores, so it should be the first 94 elements, not 92. (This is admittedly approaching eleven years old, but this is a point worth making. Np and Pu are actually more common than the really rare branch products like Pm and At.) Double sharp (talk) 11:01, 7 March 2018 (UTC)

Diagrams
--Harp 15:52, 19 January 2007 (UTC)
 * http://universe-review.ca/I14-08-elements.jpg A picture, like this were useful (universe).
 * http://rst.gsfc.nasa.gov/Sect20/A7.html On this page are not so nice diagrams (solar system, earth, sun), but it is on NASA page, these can be public domain.

Missing link/article
The section Abundance of elements in the Universe speaks about (repulsive) dark energy and (attractive) dark matter. That's fine with me, and measuring their amounts probably affects what abundance of different chemical elements we may expect in the Universe. But for anyone not accustomed to the concepts dark energy and dark matter it would be appropriate with a and a  or so, to explain the concepts. Rursus declamavi;  13:20, 14 February 2007 (UTC)


 * OK, those links exist, but I'm still discontent: it should be clearer how dark thingies affect the abundance of chemical elements. I'll take a look later, when my template-for-star-constellations are fully implemented. L8R!! Rursus declamavi;  13:22, 14 February 2007 (UTC)

Abundance of the chemical elements in organisms
That table doesn't look correct, if "number of atoms for a thousand carbon atoms" is true. The data may be correct if it is "mass per 1000 mass units of carbon". Icek 15:37, 9 March 2007 (UTC)
 * Icek is right, once I realized he wasn't objecting to the trivially true carbon figure of 1000. An organism is mostly H2O, therefore there should be more hydrogen atoms than oxygen atoms (but not more hydrogen mass than oxygen mass). Art LaPella 17:36, 9 March 2007 (UTC)
 * You are of course correct, and I completely forgot the water ;). In the dry mass, there should also be more hydrogen than carbon atoms (in carbohydrates: most common monosaccharides are C6H12O6, and chained the formula is effectively C6H10O5; in fats: the most common fatty acids contain about twice as much H as C; in proteins: 17 out of 20 amino acid rests contain more H than C). Icek 17:57, 11 March 2007 (UTC)


 * While you are correct that the body contains quite a bit of hydrogen, compounds such as Phenols and polycyclic compounds(which contain multiple carbon rings connected, requiring fewer hydrogen atoms- these are especially common in neurochemicals and hormones) found in the body help make up some of the difference. Other large concentrations of carbon can be found in bone, connective tissues and keratin. The quantity on the chart may seem low, but also remember that the chart is by mass, and carbon weighs 12 times as much as hydrogen, before one considers that a significant portion is carbon 14 and so weighs 14 times as much.--Scorpion451 02:07, 13 July 2007 (UTC)


 * "chart is by mass" - not according to the chart's labeling it isn't. Abundance of the chemical elements is labeled "atoms of the element per 1000 atoms of carbon" and "Note that this "abundance" is not the same as mass-fraction, as different elements vary greatly in mass." The table is at least mismatched with its labeling. The atom-fraction (not mass fraction) abundance in organisms should be about 50% H, 25% C and 25% O according to . Art LaPella 04:47, 13 July 2007 (UTC)

Ohhh, that chart, I was looking at the human body one. It is by ratio. Yes that chart is definatly way off. Thanks for drawing my attention to that, I know where to find more reliable numbers. See if I can't fix that.--Scorpion451 05:53, 13 July 2007 (UTC)

I couldn't find the chart I saw a while back on Nasa's website, so until someone can find the right numbers the chart should be removed from the page. I'm putting it here so we still have it, but it still needs to be corrected.-- S c or pio n4 5 1 rant 23:01, 29 July 2007 (UTC)

Organisms
The atom-fraction abundance of elements compared to carbon, expressed as atoms of the element per 1000 atoms of carbon* (taken from Mary K. Campbell, Shawn O. Farrell - Biochemistry)

* Note that this "abundance" is not the same as mass-fraction, as different elements vary greatly in mass.

Parts per million vs. percent
The first table in the article lists element abundances in parts per million and the latter two, human body and ocean water compositions, are in percent. Is there a reason for the differing representations? --dinomite (talk) 19:42, 24 November 2007 (UTC)

"Orders of Magnitude" is misused
In the elements in the universe section, the statement:

"...; oxygen has abundance rank 3, but atomic number 8. All others are orders of magnitude less common. "

is incorrect. Oxygen is only about 2 times more common than the next element down (Carbon), not "orders of magnitude" which implies a factor of 100 or more. Perhaps what is mean is that H and He are orders of magnitude more abundant than other elements. If so, this should clarified. I will go ahead an change this to "substantially lower". Feel free to improve further

Substar (talk) 03:33, 31 March 2008 (UTC)Substar

Abundance of elements in Earth's crust Graph Sucks
See [] —Preceding unsigned comment added by 99.233.80.254 (talk) 05:15, 4 June 2008 (UTC)
 * I almost reverted the above as linkspam, but I think he wants us to search thru the "Featured Articles" for a criticism of the graph. Art LaPella (talk) 06:34, 4 June 2008 (UTC)

Abundance of elements in the Universe
The first section on cosmic abundances could use some discussion of the analysed content of carbonaceous chondrites. --arkuat (talk) 03:17, 27 June 2008 (UTC)

The graphic of the elemental abundances within the solar system has no scientific references linked from the source blog (http://blog.sdss.org/2017/01/09/origin-of-the-elements-in-the-solar-system/) so should be removed. For the time being I am going to use the updated graphic from the same source, because it least has a question mark in the key, indicating the high level of uncertainty about the sources of the various elements. Madeupmike (talk) 10:43, 9 September 2021 (UTC)

Abundance of elements in universe-- mass vs. nuclei
I find these two charts (and in particular the relative amounts of Hydrogen and Helium in each) confusing. Hydrogen-1 has 705,700 nuclei per million to Helium-4 (which is 4 times heavier)'s 275,200. In both cases the other isotopes are so rare as to be negligible. Yet in the end Hydrogen still makes up more than twice as much mass as Helium. How are these numbers consistent? Kevinatilusa (talk) 00:34, 5 February 2010 (UTC)


 * Hi, the table with the parts per million is definitly misleading. The numbers in the table are the mass fractions not the nuclei per million. This should be changed! E.g. of 100 nuclei 92 are hydrogen, and 7.8 are helium nuclei, which translates into a mass fraction of 73.5 % hydrogen and 24.8 % helium... In Astrophysics we often use the tables of Grevesse, Anders, Abundances of the elements: Metoritic and solar, 1989 or newer versions
 * In the meantime I changed the parts per million in the tables to mass fraction in parts per million. MacHyver (talk) 18:14, 29 March 2010 (UTC)


 * I'm trying to find a list of element commonality in the universe, by rank, and this article was not very helpful for that. And this is ranked MID Importance?!?!? —Preceding unsigned comment added by 24.145.151.112 (talk) 00:13, 25 March 2010 (UTC)

Alternating trend
The graph of relative abundance of elements in the solar system is fascinating, but while the pattern of alternation between odd and even atomic numbers is noted in the caption, it is not explained anywhere, unless I'm missing something. What causes it? (Explanation should go in the article rather than here.) Beorhtwulf (talk) 17:07, 28 February 2011 (UTC)


 * I added a new section on "Elemental abundance and nuclear binding energy" that gives a quick explanation; follow the Wikilink to "Semi-empirical mass formula" if you want to see the gory details.Reify-tech (talk) 06:37, 2 April 2011 (UTC)


 * Excellent, thanks for adding that. Beorhtwulf (talk) 15:48, 26 April 2011 (UTC)

Cadmium, not tin
In the graphic labeled


 * SolarSystemAbundances.png

cadmium (Cd) is weirdly labeled tin (Sn).

Also, since the lines connecting the data points in this graphic are present merely as a visual aid rather than as a suggestion that some differentiable continuum occupies the interval between the data points, it would perhaps be better if, reflective of the absence of primordial technetium and promethium, the line segment between molybdenum and ruthenium and the line segment between neodymium and samarium as well as the line segments after bismuth were omitted. Rt3368 (talk) 03:57, 22 May 2016 (UTC)

Sources needed
The section on "Atmospheric elemental abundance" gives no sources, and is sketchy on data beyond the top 3 elements.Reify-tech (talk) 06:37, 2 April 2011 (UTC)

I found some potential new (to me) sources at http://www.webelements.com/periodicity/ (heavy use of Flash). Lists of elemental abundances for the Universe, Sun, meteorites, Earth, ocean, streamwater. I haven't formed any opinion on their usability yet. Any comments?Reify-tech (talk) 22:20, 2 April 2011 (UTC)

Charts and graphs
The bar chart tables and pie charts are an interesting addition, although the wide magnitude range of the abundance numbers poses a difficult challenge in presenting the data clearly. The compromise used in the Milky Way Galaxy table seems to work passably well; I hadn't realized how Neon outweighs Silicon and Magnesium combined, even though the numeric data is already right there in the table.

However, please consider removing the pseudo-3D pie charts, and using ordinary 2D pie charts instead. The pseudo-3D doesn't add any clarity, and visually distorts the information being presented. See the article on chartjunk for a bit more more on how spurious 3D can obscure the data.

Also, please do show the sources (in a footnote, if needed) for the information in the piecharts at the top of the article. Thank you! Reify-tech (talk) 22:16, 2 June 2011 (UTC)

Formatting help
I added the section on total abundancies, but cannot figure out how to get the table to display in the correct spot. Any help would be appreciated. Nick Beeson (talk) 15:37, 12 August 2011 (UTC)

The new table is quite comprehensive, but may actually be too large for the article, pushing other important information far down the page. I strongly recommend breaking the table out into a separate article, pointed to by the brief introductory text already in the article. A possible title is "Bulk (total) elemental abundance of the Earth". Alternatively, see the article Abundances of the elements (data page) which already accommodates several data tables too large for the main article; it may be better to incorporate the material into an existing table there. Either way, this resolves the formatting issue in the already-crowded main overview article. Reify-tech (talk) 16:15, 12 August 2011 (UTC)

Oceanic elemental abundance: obvious errors, looks like abundance in rock
Seawater is "On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L," (see also http://en.wikipedia.org/wiki/Abundances_of_the_elements_%28data_page%29#Sea_water which is referenced) It is mostly water! One Liter of Water equals one Kilogram by definition. In my head that comes out to be about 888 grams 16Oxygen and 111 grams 1Hydrogen per Kilo, or per Liter, of H2O.

Why is Hydrogen listed as 260 parts per million? Shjacks45 (talk) 03:46, 11 September 2011 (UTC)
 * Formatting glitch placed that table in a wrong section. Fixed. Thanks. Materialscientist (talk) 04:37, 11 September 2011 (UTC)

Carbon in Earth wrong?
I have a question that might be more appropriately addressed to the Deep Carbon Observatory, but let me start here first in case I've merely misread something.

The table in the section "Earth's bulk total elemental abundance gives silicon as 161000 ppm (i.e. 16.1%) and carbon as 730. Since Earth's mass is 5970 exatonnes (6 &times; 1024 kg), that would give carbon a mass of 5970*.00073 = 4.36 exatonnes.  That's 4.36/0.84 = 5.2 million times the 0.84 teratonne mass of Earth's atmospheric carbon.  I had no idea Earth had so much carbon.

From http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html the carbon in Venus's atmosphere is 0.480*.965*12/44 = 0.126 exatonnes, so carbon in Earth to carbon in Venus's atmosphere is 4.36/.126 = 35 times as much. If Venus has anywhere near as much carbon as Earth that would imply that much more than 90% of Venus's carbon is sequestered. At a sustained surface temperature of 740 K, remarkable.

Furthermore in the whole of Earth silicon is roughly 161000/730 = 200 times as abundant as carbon.

Yet in the next section on abundance in the crust, silicon again appears to be roughly 200 times as abundant as carbon.

The core being largely iron, this would imply that the silicon/carbon ratio in the mantle equals that in the crust.

The difference between no significant carbon in the mantle and Si/200 is about a factor of 4010/23.7 = 170. (That's the mass ratio for mantle/crust, 4010 and 23.7 being in exatonnes.)

Is there really that much carbon in the mantle? Or if not, that much uncertainty as to the real amount? --Vaughan Pratt (talk) 21:06, 11 January 2013 (UTC)

Argon-40
In the table "Most abundant isotopes in the Solar System" argon-40 is missing. AFAIK it should be slightly more abundant than iron-56, which makes it kind of important. Rursus dixit. ( m bork3 !) 10:37, 12 February 2014 (UTC)
 * Solar argon is mostly 36Ar, the alpha-process isotope, as expected from its being produced by stellar nucleosynthesis. Only when decay of 40K from rocks is the main source of Ar, like on Earth, will 40Ar dominate; and in those locations Ar, being an inert gas, is rare. Double sharp (talk) 11:08, 7 March 2018 (UTC)

Periodic Table Graphic - is it's source reliable enough?
The periodic table showing the sources of the elements is taken almost exactly from an on-line glossary from AzNU. There isn't a peer reviewed article backing it up. Its really nice information - if it can be relied upon. Aside from not having an obviously reliable source, interpretation seems to be ambiguous: are the elements being referred to in the context of meteorites (which seems a reasonable interpretation) or in terms of Universal abundance in the original source? It can't be determined by examining the on-line site. Unless someone wants to contact James Wittke or Ted Bunch (the authors of the online info) and ask them, I'm afraid that it doesn't meet the requirements for inclusion.Abitslow (talk) 18:52, 16 June 2015 (UTC) I agree, this information isn't reliable enough to be included. It would be great if there were a properly referenced one we could use, but I can't find one 2406:E003:E3E:ED01:8178:9EDA:2046:3E38 (talk) 22:55, 10 September 2021 (UTC)

Universal abundance of Lithium
In the Universal Abundance section, there are several errors with regards to Lithium. First, and how this has escaped attention is curious, Li was one of the three or four primadorial elements, CREATED IN THE BIG BANG (according to our best models). Lithium is relatively unstable (see the Wikipedia article on Lithium) and so much of the primadorial Li likely was transformed, but that is another question, and a more complicated one since it involves temperature time considerations. Most of the 1-2 % of matter not H or He made in the BB was Li. Claiming that the ENORMOUS amount made then wasn't made in "significant" quantities is misleading at best, and wrong at worst. Just as bad is the claim that Li isn't formed in stars. It certainly is. Older stars have less of it, thought to be due to its instability and mass (concentrated in star cores, above several million degrees it will transform). Younger stars have more of it (some do). It is present in cooler stars and in stars where it hasn't fallen into the core. I have a bit of difficulty that the Lithium present in the Universe today is due to cosmic rays. We need a reliable source for that claim. (I posted separately about the periodic table graphic, see above.Abitslow (talk) 19:06, 16 June 2015 (UTC)
 * The mass fraction of Li produced in BBN was actually on the order of 10−10, and certainly nowhere near 1%. Li is certainly not formed in stars: in fact they destroy whatever Li they are born with. Double sharp (talk) 09:20, 3 January 2019 (UTC)

Please slightly alter one image
The image with the label:

"Periodic table showing the cosmogenic origin of each element"

uses the term "man-made", which is inconsistent with WP:GNL, which says to avoid gender-generic "man". Any way to change it to "artificial" or something similar?? Georgia guy (talk) 14:44, 24 September 2015 (UTC)

Pie Chart is Wrong
I'm not a SME, but according to pie charts, the early universe had photons and neutrinos but today there are none. How can I be the only one that sees this obvious blunder.Bcwilmot (talk) 05:11, 1 September 2016 (UTC)
 * I'm no SME either, but what it means to me is that the total of photons and nutrinos and any other categories that might exist are less than about 0.4% of the current universe. The original graph, located at http://map.gsfc.nasa.gov/media/080998/index.html, doesn't seem to supply any more information. YBG (talk) 05:43, 1 September 2016 (UTC)

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Bar Chart Wrong
I think it's supposed to be 63 percent dark matter 13.7bya — Preceding unsigned comment added by Autumn Wind (talk • contribs) 18:38, 16 February 2017 (UTC)

Copyright problem removed
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Dark Matter?
This article is entitled "Abundance of the chemical elements." Does no one think it's somewhat irrelevant to include a chart about dark matter and dark energy as the very first graphic? Include this in a subsection by all means, but an article about chemical elements should focus on chemical elements, should it not? --InvaderXan (talk) 16:52, 10 January 2018 (UTC)
 * I agree. I moved this image to Dark matter. RockMagnetist(talk) 19:37, 10 January 2018 (UTC)

Biological requirement chart colors
In the periodic table chart indicating biological requirements, there are four shades of green, which makes the chart somewhat harder to read than using more clearly distinct colors. Any ideas about how to improve the color scheme? One point that I would note is that about eight percent of men have red-green color blindness, which would mean that some combinations of red and green would not be much improvement from the current four shades of green for a significant number of users.

Is there reason enough for the current color scheme to discuss a change, or should I just go ahead and be bold?
 * —Steve98052 (talk) 23:32, 20 August 2018 (UTC)
 * There is nothing inherently wrong with using different shades of the same color. The main thing is to communicate that this is a hierarchy of biological importance, so a sequential color scheme should be used. Here is a good example, part of a web site that offers color sequences based on research on perception. RockMagnetist(talk) 17:42, 21 August 2018 (UTC)
 * The main thing you want to avoid is rainbow color schemes. RockMagnetist(talk) 17:43, 21 August 2018 (UTC)
 * Fair point, but the specific four shades of green are quite indistinct on my screen. Maybe a different selection of shades would be an improvement. — Steve98052 (talk) 20:32, 21 August 2018 (UTC)
 * As far as I am concerned, you are welcome to play with the color schemes. I tried an all-green one and didn't like it. RockMagnetist(talk) 16:03, 22 August 2018 (UTC)
 * I have increased the difference between chromium and essentials slightly. Cause that's where it differed the least for me. --Jzandin (talk) 10:15, 18 January 2020 (UTC)
 * That's an improvement. Interesting that chromium has its own color. RockMagnetist(talk) 21:25, 19 January 2020 (UTC)

I belatedly realized that this discussion should really be at Template talk:Periodic table (nutritional elements). We're discussing a template that is used in over 100 articles. I have transcluded this discussion over there so we can continue talking here. RockMagnetist(talk) 16:03, 22 August 2018 (UTC)

Significantly more iron?
The section Mantle says "The mantle differs in elemental composition from the crust in having ... significantly more iron" But then lists iron at 5.8%, while the above section Crust lists the crust as having iron at 5.6%. Could someone rectify or at least shed light on this inconsistency? --RProgrammer (talk) 07:54, 9 July 2019 (UTC)
 * Clearly not true, and I will delete that sentence. Also, there is no source for the mantle numbers. There are different models for the elemental composition, and the numbers will depend on whether we're talking about the primitive, enriched or depleted mantle, not to mention upper and lower mantle. RockMagnetist(talk) 18:43, 27 April 2020 (UTC)r

Human body
It seems odd to focus on the human body and not on life in general. In particular, CHNOPS is a concept that is used for life in general, and does not represent the six most abundant elements in the human body. RockMagnetist(talk) 18:47, 27 April 2020 (UTC)

Iron-56
The description of iron-56 in this page contradicts the description on the Iron-56 page. I am sure the description on the iron-56 page is correct. In particular this page says

"Iron-56 is particularly common, since it is the most stable nuclide (in that it has the highest nuclear binding energy per nucleon)"

On the Iron-56 age it says

"Of all nuclides, iron-56 has the lowest mass per nucleon. With 8.8 MeV binding energy per nucleon, iron-56 is one of the most tightly bound nuclei.[1]

Nickel-62, a relatively rare isotope of nickel, has a higher nuclear binding energy per nucleon; this is consistent with having a higher mass-per-nucleon because nickel-62 has a greater proportion of neutrons, which are slightly more massive than protons. (See the nickel-62 article for more)."

I was not confident enough of my understanding of this to try to correct the text in this section. Hope someone else can! Holland jon (talk) 18:34, 16 October 2020 (UTC)