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Article changed over to new Wikipedia:WikiProject Elements format by Dwmyers 14:39 Feb 26, 2003 (UTC) and Mkweise. Elementbox converted 14:39, 2 July 2005 by Femto (previous revision was that of 17:16, 30 June 2005).

Information Sources[edit]

Some of the text in this entry was rewritten from Los Alamos National Laboratory - Chromium. Additional text was taken directly from USGS Chromium Statistics and Information, USGS Periodic Table - Chromium, from the Elements database 20001107 (via, Webster's Revised Unabridged Dictionary (1913) (via and WordNet (r) 1.7 (via Data for the table was obtained from the sources listed on the subject page and Wikipedia:WikiProject Elements but was reformatted and converted into SI units.

Dietary Sources of Chromium[edit]

There needs to be a discussion about the dietary uses of chromium and food sources.

Indeed. Some mention might also be made of Erin Brockovich.
Here's a fairly good digest of mineral nutrition. I've reproduced the Cr section below:
It is difficult to estimate the chromium requirement, but a range of 50 micrograms to 200 micrograms per day is tentatively recommended.
Trivalent chromium is required for maintaining normal glucose metabolism. Evidence shows that chromium improves glucose tolerance [Riales, R., & Albrink, M. J., American J. Clin. Nutr., Vol. 34, pg 2670] . Diabetes and coronary heart disease are associated with low chromium concentrations in human tissue.
The chemical forms of chromium in foods are not known with certainty, but the bioavailability of chromium compounds has been found to be high in brewer's yeast, shell fish, whole wheat bread and mushrooms.
An increased incidence of bronchial cancer has been associated with exposure to dusts containing chromate. But the carcinogenicity of certain chromates bears no relevance to the nutritional role of non toxic trivalent chromium.
Other sources I've found list:
  • organ meats
  • brown rice
  • wheat
  • eggs
  • orange juice
  • potatoes
  • Cheese
  • Corn oil

I imagine one could also scrape the sides of stainless steel cookware more often.--Joel 06:06, 7 Jun 2005 (UTC)

Dakota~N~Kat Forever Happy Valentines Day to all!!!


What does "lucious" in Notable characteristics mean?--Warut 11:50, 10 November 2006 (UTC)

Lustrous, I presume, referring to its luster - or else it's just lusty stuff :-) Vsmith 12:28, 10 November 2006 (UTC)

What does Chromium look like when it reacts to a different element?--DK 12:52, 14 February 2008 (UTC)

I believe there is a problem with the electronic configuration, it is shown as 3d5, 4s1: i believe it is 3d4 4s2

Then you might have to consider reëxamining your beliefs, because it is actually [Ar] 3d5 4s1. Not all elements obey the Aufbau principle. Double sharp (talk) 14:14, 12 November 2013 (UTC)

glass ware[edit]

Is anybody still using this stuff or was it only substituted here in Europe by sulfuric acid hydrogen peroxide mixtures?--Stone 10:54, 4 April 2006 (UTC)

Yes, in the U.S. they are still currently using Chromium for all sorts of jobs.--DK 1:02, 14 Febuary 2008 (UTC) —Preceding unsigned comment added by (talk)

Question about units of measurement?[edit]

I'm not sure what a "µg" is. If I'm not sure, I'm guessing some others aren't either. Maybe someone could clear this up here and in the article if it needs it? 11:51, 5 April 2007 (UTC)

You're from the US, right? Don't worry, they'll catch up sooner or later. :) It's micrograms, micro (µ) is a common prefix in the International System of Units. I've added a link in the article. Femto 14:41, 5 April 2007 (UTC)

Biology: Chromium, Bioavailability and Cancer[edit]

Certainly, there are no studies on cancer and uptake of hexavalent chromium thru skin or GI tract. But hexavalent chromium is carcinogenic, and is penetrating easily the skin. It is not correct to conclude only from the fact that no clinical / environmental studies on cancer other than lung are available that it would not have an carcinogenic effect. To make it clear, the dosage is important for the generating of cancer. However from the nutritial point of view one would not expect to exceed this dosage.

National Institute for Occupational Safety and Health, USA NIOSH Safety and Health Topic: Chromium (Chromium IV, Chromic (VI) Acid, Chromates (VI))

Baranowska-Dutkiewicz B.(1981) Absorption of hexavalent chromium by skin in man. Arch Toxicol. Mar;47(1):47-50.

Kerger BD, Paustenbach DJ, Corbett GE, Finley BL, (1996) Absorption and elimination of trivalent and hexavalent chromium in humans following ingestion of a bolus dose in drinking water. Toxicol Appl Pharmacol. Nov;141(1):145-58.

Dutkiewicz T, Baranowska-Dutkiewicz B, Konczalik J. (2000) Percutaneous absorption studies after forty years. Int J Occup Environ Health. Apr-Jun;6(2):111-3. Robi123 21:32, 6 May 2007 (UTC)

According to UC Berkeley Professor Nancy Amy, Chromium is carcinogenic. Source: 16:30 in class "19: Trace Minerals" in online course "NS 10: Introduction to Human Nutrition", available on iTunes via [[1]].Robi123 19:44, 11 May 2007 (UTC)

Shouldn't Chromium also be in Category:Biology and pharmacology of chemical elements ? Eldin raigmore (talk) 18:49, 16 May 2009 (UTC)

Chromium Nicotinate[edit]

What is "Chromium Nicotinate"? It is on the ingrediant list for Spava Coffee's "Metabolism Coffee". Is it a a mix of Chromium and Nicotine? Chromuim and Nickel? Is there any research on it? Thanks Antmusic 15:10, 7 August 2007 (UTC)


What are some chemical properties of chromium?Potterfa11 (talk) 22:05, 14 January 2008 (UTC)


Chromium is often used because it's 'shiny' so some hard values on the material's reflectance would be nice. would help in computer graphics as well Dan Frederiksen (talk) 05:34, 14 April 2008 (UTC)


It says it was discovered in 1974...that seems like a mistake. —Preceding unsigned comment added by (talk) 19:55, 8 July 2008 (UTC)

It wasn't actually a mistake. The 1974 date was referencing when the artifacts were found. However, it was poorly worded to easily confuse. I changed it to be less confusing. Wizard191 (talk) 02:48, 9 July 2008 (UTC)

Disambiguation for Chromium/Google Chrome[edit]

Because of the Chromium open source project (highly in the news lately along with its flagship implementation, Google Chrome) I added a disambiguation for "Chromium (web browser)". Because the main article is named "Google Chrome" this was unfortunately changed to a link to "Google Chrome", then deleted because it was not similar enough (which is obviously true). However many users may search for Chromium, and should be redirected to the main article which describes both Chromium and Google Chrome. Please provide any input you may have here before removing this again. sHARD (talk) 14:31, 4 September 2008 (UTC)

I switched to linking to a disambig page to handle additional meanings of chromium as well. This should handle the situation well. -- Ed (Edgar181) 15:21, 4 September 2008 (UTC)
Looks good to me sHARD (talk) 15:55, 4 September 2008 (UTC)

Electron configuration[edit]

We all know that even though the expected electron configuration of Chromium would be [Ar] is shown to actually be [Ar]4s13d5

My chemistry textbook says this exception to the sequence in which orbitals are filled is still largely unknown and the reason for the anomaly is still disputed amongst chemists

I'm not too well researched in the dispute or the possible explanations, but wouldn't it be a key part of this article? Shouldn't it be brought up, maybe given it's own section?

Does anyone know where I can learn more about the research being done on chromium's and copper's anomalies?-Aspiring chemist (talk) 21:51, 16 November 2008 (UTC)

electron configuration in the table[edit]

Why is it [Ar]3d54s1 in the table?Asoer (talk) 01:30, 21 November 2008 (UTC)

I don't know, it should be [Ar]4s3d^5. Landfieldjc (talk) 16:54, 25 January 2012 (UTC)

Chinese atomic theory?[edit]

In the history section the wording is such that the chinese discovered this element, which is misleading, unless they had an atomic theory and categorized the material they discovered as a chemical element. It is also misleading becauser there is no indiciation that the knowledge was transfered to the westerners, but rather that later archeological discoveries have revealed this chrome plating or similar to be a hidden knowledge, much later to be independently discovered by westeners. This is not like iron, which was discovered before antiquity, and the generally known knowledge of iron was transfered to the "western civilization", later to be classified as a chemical element. Chromium was rediscovered in West, and needs a (re)discoverer. The element was classified as a chemical element in the west, and if that was by Vaquelin, then he is a discoverer. Chinese allegations aside (unless they can provide a similar Chinese record). ... said: Rursus (bork²) 10:45, 9 January 2009 (UTC)

Chromium and oral health[edit]

Hodges SJ, Spencer RJ, Watkins SJ. Unusual indelible enamel staining following fixed appliance treatment. J Orthod. 2000 Dec;27(4):303-6

Ç. Türksel Dülgergil, Ebru Olgun Erdemir, Erturul Ercan, and Ali Erdemir An Industrial Dental-Erosion by Chromic Acid: A Case Report Eur J Dent. 2007 April; 1(2): 119–122.

Gomes ER. Incidence of chromium-induced lesions among electroplating workers in Brazil. IMS Ind Med Surg. 1972 Dec;41(12):21-5. —Preceding unsigned comment added by (talk) 20:39, 2 April 2009 (UTC)

Acidic oxide?[edit]

This page says that Cr has a solely acidic oxide whereas Chromium(III) oxide claims to be amphoteric. Which is correct? Alecjw (talk) 09:15, 16 June 2009 (UTC)

acidic means that if you put it into water the pH is between 1 and 7, while amphoteric means the molecule is able to act as base in acidic medium while it reacts as a acid in basic medium. For example HSO4- is a relative strong acid, but in acidic conditions you can reprotonate it to become H2SO4 sulfuric acid or deprotonate it to become a SO42- sulfate ion.--Stone (talk) 13:03, 16 June 2009 (UTC)

Electronic Configuration:[edit]

Reasons for Chromium's electronic configuration of 3d5 4s1: 1. Hund's rule of maximum multiplicity states that half filled orbitals have maximum spin and hence lower the energy level, making the atom more stable. 2. in carbon in that case it should be 2s1 2p3. but the energy required for carbon to excite( in the sense shift) an electron from 2s to 2p is more than the energy lowered by the p3 half filling stability. 3. 3d and 4d have only a little more energy than 4s and 5s respectively. hence, the shifting is possible. Even in Cu (Cooper) the configuration is 3d10 4s1 not 3d9 4s2 because of the same reason. (talk) 14:01, 11 October 2010 (UTC)RohanShankar

For lack of a better word, this is BS that just happens to work for the 4th period. There is a lot more going on than that and you are not going to be able to predict the electron configuration without a lot of calculation. Since the 4th period of transition metals is usually the first one covered in schools it is taught as a kludge that works, just like sloppy Aufbau. How does this explain Ru's configuration of [Kr] 4d7 5s1, or (even more funnily) W's configuration of [Xe] 4f14 5d4 6s2? Double sharp (talk) 14:13, 12 November 2013 (UTC)

Abundance in groundwaters[edit]

The last paragraph of the 'Occurance' section states:

"..although in some areas the ground water can contain up to 39 µg of total chromium of which 30 µg is present as Cr(VI)"

µg per what? µg/mL is a lot, wheras µg/m³ is tiny. Or is that µg in total, everywhere? I'd alter this myself, but am uncertain about my wiki-editing skills and have no desire to muck up a Good Article. I note that the claim is cited, so there's an assumption that the true units are in there someplace.


PS... it's litres (LEE-ters), not liters (LIE-ters) ;-) (talk) 10:57, 1 February 2011 (UTC)

Done! its µg/L --Stone (talk) 22:25, 1 February 2011 (UTC)


1. Occurence; see Peridotite: "Minor minerals and mineral groups in peridotite include plagioclase, spinel (commonly the mineral chromite)"; I was thinking of Chromium mines in the San Juan Is. and Olympic Penninsula (used in WWII). Aside: the City of Seattle Arborist (Marv Black dec.) noted that the high Chromium content of some forest soils in the Bellingham/Lake Chelan led to stunted tree growth and excellent Bonsai.

What I could find: Olympic Penninsula was mostly manganese mining;

2. K
or K3[Cr(CN)5NO] as +1 : the German reference doesn't Google except for references to your wiki page. Metal nitrosyl complex information doesn't match +1 designation if only because it seems to violates the section on bonding and symmetry. I've got a text on advanced inorganic chemistry for a post grad course I took but ...

This is real, the structure shows linear CrNO, which indicates NO+ and therefore Cr+, 17e-.
The book gives that structure.

3. Natural Cr(VI)??? I did environmental water testing for several years. EPA Chromium in water is usually tested by AA or ICP, Standard Methods described Hexavalent chromium test using diphenylcarbazide, not usually done due to expense/time consuming. Cr is then reported as Cr(VI) leading to this erroneous statement. Subsoil is usually acidic and anaerobic, and does not spontaneously generate Cr(VI). It accelerates corrosion of stainless steel and our lab did a fair number of gas station remediation testing (30 year SS Tanks only last about 15 years underground.)(Put a cast iron bolt and a stainless steel fork in separate pickle jars: the bolt will be rusty and the SS fork will dissolve.) EPA Region X library in Seattle had studies of reports of "natural" Cr(VI) and it could not be recreated under identical conditions. This included air oxidation of sea water (pH=8.4). In freshman lab we add peroxide to Chromite solution to make Chromate but (like Aluminate) the Chromite solution is pH=12 or higher. I don't think caustic soda lakes in the desert get that high, above 10 and you absorb carbon dioxide from the air.

I agree that natural Cr(VI) seems unlikely in nature, but the statement is backed with a ref to a published study. It would be helpful to find a publication that states that Cr(VI) is highly unlikely to be of concern.
doi:10.1073/pnas.0701085104 would this be an acceptable ref?

4. Dermatitis to Stainless Steel is usually attributed to Nickel allergy which affects women disproportionately (e.g. earrings with SS posts, SS flatware).

A ref would help, but we need to examine such comments.

5. I appreciate Cr(VI) toxicity however I remember that Potassium Dichromate "mouthwash" was sold OTC for dental diseases at Bartell's and Rexall drug stores. Found some obscure Formularies on Google books from 1907 and 1921, but I remember seeing it in the drug store as late as the 90's.

Amusing. Again a ref would help. The section starting "In 2010, the Environmental Working Group studied..." is preachy in a way.
sodium dichromate mouthwash

6. Chromium doesn't actually "replace" Aluminum in Ruby as the Al occupies tetrahedral space and Cr occupies an octahedral position. (Similar to Iron colorant; same Fe+3 in Amethyst and Citrine, difference is octahedral to tetrahedral).

Al is not typically tetrahedral in its oxides, which one can barely figure out reading our unclear article aluminium oxide.

Amythyst is quartz (SiO2) wherein Fe(III) occupies Si sites, I am pretty sure. Not sure how change balance is maintained, maybe OH for O.


7. Tried to add Hexavalent chromium in "see also" but doesn't connect? Redirected?

8. Glass is commercially colored green by iron (ferrous). Refractory Chromium oxide is an opaque green glaze.

Cr(III) is indeed used as a glaze component as well as a colourant for glass, according to my source.

9. Copper Chromite is an important hydrogenation catalyst.

yes, an oversight. I started a section on catalysis.
Really helpful comments BTW. Do other elements...
Nice work! Hope for more!

Shjacks45 (talk) 06:45, 26 August 2011 (UTC)

--Smokefoot (talk) 13:01, 26 August 2011 (UTC)
--Stone (talk) 20:40, 26 August 2011 (UTC)

File:Chromium crystals and 1cm3 cube.jpg to appear as POTD soon[edit]

Hello! This is a note to let the editors of this article know that File:Chromium crystals and 1cm3 cube.jpg will be appearing as picture of the day on December 14, 2011. You can view and edit the POTD blurb at Template:POTD/2011-12-14. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page so Wikipedia doesn't look bad. :) Thanks! howcheng {chat} 17:12, 13 December 2011 (UTC)

Picture of the day
Chromium crystals and cube

Crystals of pure chromium created by a chemical transport reaction, along with a cube of the element for comparison. Chromium is a steely-gray, lustrous, hard metal that has high corrosion resistance and hardness. Its major industrial uses are in electroplating and making stainless steel.

Photo: Alchemist-hp
ArchiveMore featured pictures...


Under the section Passivation, it says that oxygen forms an oxide layer a few turds thick. I am unaware of any unit of measure called a turd, and wiki brings up feces when I search for the word turd. I would guess its vandalism, but that's just me. — Preceding unsigned comment added by (talk) 16:04, 5 January 2012 (UTC)

Fixed, thanks. Vsmith (talk) 16:11, 5 January 2012 (UTC)

Is it Chromium(III) or Chromium(VI) that's used in stainless steel?[edit]

Subject says it all really. The article doesn't make this clear, and I was wondering if someone could clarify. Thanks. --Rebroad (talk) 00:44, 20 January 2012 (UTC)

It isn't both used in stainless steel. You have metalic chromium (= Chromium(0)) used in stainless steel. --Alchemist-hp (talk) 01:43, 20 January 2012 (UTC)

typical charge on a single atom of chromium[edit]

this is useful information that is too hard to find- I just looked elsewhere. the typical ion configuration is more important that in being used in electroplating on bumpers... duh — Preceding unsigned comment added by (talk) 04:33, 13 March 2012 (UTC)

Wrong confugration description[edit]

Isn't it the other way around? It says now on the table on the side: 4s^1,3d^5 It is the wrong order . First write the lower level and then the higher one. It should be, I think: 3d^5 then 4s^1, giving 3d^5, 4s^1 — Preceding unsigned comment added by (talk) 07:52, 20 April 2012 (UTC)


The 1st sentence of the last paragraph in the intro section (to wit: "Trivalent chromium (Cr(III)) is required in trace amounts for sugar and lipid metabolism. ") seems to contradict the "Biological Role" section.

Most evidence in refs 46-50 seems to indicate possible roles for Cr III in lipid and carbohydrate metabolism, as well as a potentiation effect on insulin action. Some of these conclusions seem to be undergoing review, however it seems premature to flatly state "Chromium has no verified biological role and has been classified as not essential for mammals.", even if there is one reference, contradicting others, that supports at least the last part of that statement. — Preceding unsigned comment added by Ggpauly (talkcontribs) 01:18, 6 September 2012 (UTC)

"Came to attention"?[edit]

The text seem to allege that the early Chinese usage of chromium indirectly led westerners on the track of a more systematical use of chromium – the key phrase is "came to attention". I don't believe so. I believe westerners "rediscovered" the metal independently. Or the westerners "discovered" it as a chemical element, unless the Chinese had a theory of chemical elements too. Not being too West-centric is a good thing, but a discovery includes full knowledge about the inner workings of ones own findings. Rursus dixit. (mbork3!) 03:45, 4 January 2012 (UTC)

The history reads as though the Terracotta warriors had chromium-plated uncorroded weapons, which is nonsense. This isn't in the lede, but the lede is still rather too detailed on this issue for a lede. Yes, it needs fixing. See discussion. SBHarris 03:55, 3 October 2012 (UTC)
A documentary TV program i saw, (may have been Nova), claimed the chinese had chromium stainless steel circa 950 AD Song dynasty; i'll try finding a reference. -- (talk) 16:53, 19 July 2013 (UTC)


File:Cut Ruby.jpg, caption: "The red colour of rubies is from a small amount of chromium(III)"
  • I changed the caption, chromium(III) is green. A citation is needed.
File:Muscovite-150242.jpg, caption: "Fuchsite, a chromium(III) bearing muscovite var."
File:Chlorid chromitý.JPG, caption: "Chromium(III) chloride hexahydrate ([CrCl2(H2O)4]Cl·2H2O)."
File:Spodumene-21687.jpg, caption: "Hiddenite (a chromium bearing spodumene var.)*
  • Although anhydrous chromium(III) is violet.
File:Chromium(III)-chloride-purple-anhydrous-sunlight.jpg, caption: "Anhydrous chromium(III) chloride (CrCl3)."
--Chris.urs-o (talk) 03:06, 6 April 2013 (UTC)

chromium is a element that is used for jhfekjwafneruy2wqdxnolmrbe qiupnsiuy43qfdr gbeuywq[xfmepiuwqdkyr431isl.dwoq — Preceding unsigned comment added by (talk) 17:38, 17 March 2014 (UTC)

Wrong Mohs hardness values probably taken on the net[edit]

I just saw that Chromium was listed on this article as 8.5 on Mohs scale. Something is wrong on wikipedia: look at Osmium's Brinell hardness value listed on the dedicated article, 3900 MPa . Molybdenum's Brinell hardness is at 1500 MPa. Tungsten's Brinell hardness is listed on wikipedia as being 2570 Mpa. Now look at the value for chromium: 1120 Mpa. It is impossible that tungsten is a "7" on Mohs scale and chromium a "8.5" given their respective Brinell hardness. Strangely here on wikipedia we have odd Moh values taken who knows where and Vickers & Brinell values whose sources are unidentified yet. I highly suspect the source for the erroneous Mohs hardness values for metals seen here, comes from , values that probably were then spread out in the wild through various blogs and websites especially in articles entitled "what is the hardest metal" which list even ceramics and composites as "metals" in their poorly written pages. (talk) 05:23, 30 September 2014 (UTC)

OK, thanks for posting this explanation. I'm sorry for reverting you: I checked the talk page before doing so, but your comment didn't show up for some reason (did you forget to save? the timestamp shows a later time than my revert). Looks like we need to check these Mohs values and get rid of the spurious ones. I have some doubts that they should be listed at all, BTW – Mohs is a nonlinear scale, so it's not clear what fractional values mean, and I gather it is not in much use in metallurgy (isn't it a mineralogical thing?). Double sharp (talk) 08:36, 30 September 2014 (UTC)
Mohs scale not being linear doesn't mean that an inferior Brinell value will give a higher Mohs value than for a material with a higher Brinell hardness value (such as tungsten for example) . Mohs scale is -not- a scale with values that are inversely related to either Brinell or Vickers! Not being "linear" is just a laymans term translating the fact that Mohs follows an exponential law , nothing else. Now to find the correct values, the real problem... (talk) 12:45, 30 September 2014 (UTC)
I didn't mean that: I agree with you that Mohs goes in the same direction in Brinell or Vickers. What I meant is that since Mohs isn't linear, it's not clear what a value like "8.5" even means. Double sharp (talk) 13:23, 30 September 2014 (UTC)
Seems like almost all the studies that mention chromium's hardness only do so in a context of microhardness of various types of chromium platings . If you read this 1993 government research paper ( ) hard chromium platings between 0.5 and 500μm thickness reach 1120 HV (Vickers) microhardness ( pages 933 934). Interestingly, electroless nickel platings reached even higher hardness values such as 1300HV (compare with actual value proposed on wikipedia ...) . Concerning research a bit more recent, a 2011 study ( ) shows that the highest hardness value for hard chromium plating is the same value again of .. 1120 HV 0.025 . To have a clue how to translate more or less precise vickers, brinell, rockwell, knoop hardness values to an approximate mineral hardness value in Mohs scale, you need to check charts in engineering books or online such as on page 721 of the document available on the official website of the Mineralogical Society of Great Britain and Ireland pertaining to the correlation between Mohs (very imprecise scale) and Vickers values and what they really represent in terms of material testing . Note that for a mineral rated with a given Mohs value, the actual Vickers hardness depends on the angle at which the sample is tested which is evident. For metals this problem is not as much of an issue and exposing metal to various angles will not yield dramatically different values. Look at this modern industrial reference chart comparing Mohs scale and Vickers hardness values . A quick estimation would place a 1120 HV Vickers hardness value in the 7-7.5 hardness range, and that is only for an extremely thin section of material in form of a plating, not bulk material. Being in the 8.5 Mohs range would mean to have a Vickers hardness circa 1900 HV which is far from being the case for chromium either in plating or bulk anyways. Hope this helps. — Preceding unsigned comment added by (talk) 00:22, 4 October 2014 (UTC)