Talk:List of oxidation states of the elements

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use this link Nergaal (talk) 19:18, 25 December 2007 (UTC)

Disagreement with CRC Press[edit]

There are many differences from the CRC press periodic table's list of oxidation states Are they listing common or all? How did we select which to label common? —Preceding unsigned comment added by Lucent (talkcontribs) 04:29, 22 December 2008 (UTC)

They are only listing the more usual oxidation states. Our list is based on Greenwood & Earnshaw (see the ref. at the bottom), which is much more comprehensive, with only a few extra oxidation states added (each addition is clearly labeled and referenced). The oxidation states that are labeled here as "common" are the ones labeled as common by G&E. I think it is safe to bet that no new "common" oxidation states will be discovered--all new discoveries are pretty exotic. --Itub (talk) 15:05, 22 December 2008 (UTC)

Astatine +7[edit]

Are we sure about this?

This indicates that AtO4- doesn't exist, and because of the inert pair effect and lack of references, AtF7 seems unlikely. —Preceding unsigned comment added by Kazyan1 (talkcontribs) 05:32, 9 May 2010 (UTC)

actually exists; however, not many books mention it, for reasons discussed at Talk:Astatine. AtF
isn't known yet AFAIK. Double sharp (talk) 10:12, 16 June 2012 (UTC)

Fractional oxidation states[edit]

We need a good way to show these. E.g. for O, we have, just listing the obvious ones: −½ (superoxides), −⅓ (ozonides), +½ (dioxygenyl). Doubtless C has a lot more, as another example. Double sharp (talk) 12:07, 13 October 2013 (UTC)

Thulium(IV) - probably incorrect[edit]

The reference quoted for this pradyot patnaik's handbook of inorganic chemicals- yes he does say that +4 compounds are known (unreferenced) - but he is alone in this as far as I can tell. For example a recent review of Ln(IV) compounds in the Encyclopedia of Inorganic and Bioinorganic Chemistry DOI: 10.1002/9781119951438.eibc2033 does not mention Tm(IV) at all. To include this we need a reliable corroborative referenceAxiosaurus (talk) 10:50, 22 March 2014 (UTC)

I've removed it here, pending reliable corroborative references. I see the Tm(IV) claim is already marked as "dubious" in Thulium#Chemical properties. Double sharp (talk) 14:21, 22 April 2014 (UTC)
Tm(IV) was claimed in 1982 in Cs3TmF7 (see [1]). This article (in Russian; English abstract) also mentions Sm(IV), Fe(VII), Fe(VIII), Ag(V), Co(VI), and Cf(V); however, Fe(VII), Fe(VIII), and Ag(V) have subsequently been refuted, Cf(V) seems to be controversial, and I don't know much about Co(VI) or Sm(IV).Burzuchius (talk) 20:44, 8 March 2015 (UTC)

Some questions[edit]

Here are some cases where I am in doubt.

Boron. There are borides, so there should be negative oxidation states of boron. In the history of the article, B(−1) was once added and then deleted. There is MgB2, and if it has B(−1), it satisfies the Zintl–Klemm rule, since the atoms of boron form the structure of graphite and graphite is a form of carbon. However, AlB2 also has this structure, so it has Al(+2)? Or is it an electride?

MgB2, according to [2], p. 183; [3], p. 315; and [4], can indeed be considered a Zintl-like compound containing B(−1). (However, I am under impression that all conducting compounds except ionic liquids may be regarded as electrides; in this case, metallic Na is Na+e, graphite is C+e (three electrons go for covalent bonds, one for conductivity), and MgB2 is Mg2+B02•2e.) I think that boron has −3 in CrB in FeB, since boron atoms in these compounds form sulfur-like chains, but I haven't find any source stating so. For −5, see below. Boron can also have fractional oxidation states, e.g. in CaB6 (LaB6 has a similar structure, so it may be regarded as an electride, see [5]). Burzuchius (talk) 11:51, 13 March 2015 (UTC)
Now I think that regarding graphite as an electride is not a good idea and MgB2 is a valid example of boron(−1). Added MgB2. AlB2 is perhaps something electride-like. Burzuchius (talk) 16:39, 21 May 2015 (UTC)

Chlorine(+2, +6). Greenwood&Earnshaw mention them in the table, but in what compounds do they occur? ClO⋅ and Cl2O2 have Cl(+1) and O(−1). For Cl(+6), a widely cited example is Cl2O6, but according to the Wikipedia article Dichlorine hexoxide, it is actually a chlorine(V,VII) oxide, and ClO3 is an error.

Good question, and I don't know the answer; but judging from the title, this article mighr help. Double sharp (talk) 14:30, 1 March 2015 (UTC)
ClO3 actually exists. Added a note.Burzuchius (talk) 15:56, 25 March 2015 (UTC)
For Cl(II), there is an article about ClF2: [6].Burzuchius (talk) 21:23, 25 March 2015 (UTC)
Some information about ClO, BrO, and IO: [7], [8], [9], [10], [11]. I am in doubt whether the oxidation states in these radicals should be considered +2 and −2 or +1 and −1. Burzuchius (talk) 13:45, 31 July 2015 (UTC)

Tellurium(+5). Again, Greenwood&Earnshaw mention it in the table. But they do not mention any compounds of Te(V). Ditellurium decafluoride (Te2F10) is an error. However, I have found an article called Tellurium(V). A Pulse Radiolysis Study and also similar articles about arsenic(IV) and selenium(V). Are they valid?

I think they're valid. Added As(IV) and Se(V), as well as an explanatory note for Te(V). Double sharp (talk) 13:38, 3 March 2015 (UTC)

Xenon(+1). The formula Xe+[PtF6] for xenon hexafluoroplatinate is probably an error. Possibly xenon hexafluororhodate is a similar case.

Since the XeRhF6 article says it's analogous to XePtF6, I think it's problably also not xenon(+1), by the same argument: Xe+, being a radical, would either dimerize or abstract a fluorine atom to give XeF+. So I think we should remove xenon(+1), and have an explanatory note stating the status of these two compounds and why xenon(+1) is excluded. Double sharp (talk) 14:30, 1 March 2015 (UTC)
Done. Burzuchius (talk) 14:51, 2 March 2015 (UTC)
There is some information about XeF: observed [12], disputed [13], then some other data appeared [14] — is it an exciplex or not necessarily? Burzuchius (talk) 16:39, 21 May 2015 (UTC)

Barium(+1). In barium platinides, BaPt, Ba3Pt2, and Ba2Pt, the reported oxidation states of platinum are −1, −1.5, and −2 respectively. So barium should have +1. Or are these compounds electrides?

Ba2Pt is an electride (Ba2+)2Pt2−·2e, according to Jansen's 2005 paper. Double sharp (talk) 14:21, 1 March 2015 (UTC)

Hafnium(+1). I have added an article about HfBr, but I cannot exclude the possibility that it is an electride like ThI3 or Lu monochalcogenides. However, there is also an article about hafnium monohalides in the molecular phase (see also [15]). So, which article is valid?

Iridium(+7). Has IrF7 actually been synthesized? However, Ir(+7) is also mentioned in something else. Burzuchius (talk) 13:18, 24 February 2015 (UTC)

Changed the ref for Ir(+7) to mention [(η2-O2)IrO2]+ instead. Double sharp (talk) 10:15, 3 March 2015 (UTC)
Additionally: Ti(−1) and Zr(−1) are often mentioned in bipyridine complexes, but, according to this paper, they should in fact be Ti(+3) and Zr(+4).
In that case, I think the mentions of Ti(−1) and Zr(−1) ought to be removed. Double sharp (talk) 15:16, 2 March 2015 (UTC)
Done. Burzuchius (talk) 21:36, 2 March 2015 (UTC)
Is platinum(+3) a common oxidation state? Burzuchius (talk) 14:36, 24 February 2015 (UTC)
Pt(III) is uncommon. Unbolded. Burzuchius (talk) 14:51, 2 March 2015 (UTC)
Sc, Y, lanthanides, and Ac. AFAIK most seemingly divalent compounds of these elements (except Sm, Eu, Yb and in some cases Nd, Dy, Tm) have electrons in the conduction band. If we do not consider them to be electrides, then Lu(II) and La(I) (for LaI) should be added. But if we do, then La(II) and Gd(II) should possibly be excluded. Holleman&Wiberg's book does not mention them, however, this review (in Russian; information in English) does (has it been refuted?). Ce(II) and Pr(II), according to Holleman&Wiberg, appear only in alkaline earth solutions. Webelements mentions CeF2 and PrF2, but I haven't found information about them anywhere else. Sc(II) AFAIK exists in CsScCl3. Y(II) is mentioned in the same review as La(II) and Gd(II). This article mentions Y(+2) and Y(+1) in the gas phase. For +1, ScCl, YCl, LaCl, GdCl, and TbCl are sometimes mentioned, but are these formulas correct? Greenwood&Earnshaw say that these compounds should also contain hydrogen. The Wikipedia article Lanthanide states that LaI is the only known monohalide. For sesquichlorides I don't know, whether they contain fractional oxidation states, mixed oxidation states, or are electrides.
As for alkaline earth solutions, [16] lists all lanthanides except Pm and Lu; but Holleman&Wiberg's book lists all except La, Gd, Lu. La(II) and Ce(II) have also been observed in some organometallic compounds; see [17] (p.332), [18], [19], [20], and [21]. Burzuchius (talk) 20:44, 8 March 2015 (UTC)
As for HfBr, it is a conducting substance, like ZrCl, ZrBr or HfCl; however, I have never found mentioning it as an electride. Burzuchius (talk) 18:11, 1 March 2015 (UTC)
I am not sure if there exists ScCl, but here are some articles about Sc(I): [22], [23]. Burzuchius (talk) 20:09, 4 March 2015 (UTC)
Sc(I) and Sc(II) have been observed in some organometallic compounds. Added examples to the article Scandium. Burzuchius (talk) 20:44, 8 March 2015 (UTC)

Lead(−3). The compound Ba5Pb3 has been reported to contain [Pb2]6−, for example: [24]. But in the article [25], Ba5Pb3 was refuted and discovered once again, with a different crystal structure. If you have access to the article, please tell me whether the ionic structure of Ba5Pb3 is still valid. Burzuchius (talk) 21:31, 3 March 2015 (UTC)

Ca? It is interesting! I have found also these articles: [26] about Sr and Ba and [27] about Ra and actinides. By the way, physicists deal with such ions as He2+, Ca6+, Ca10+, or Dy66+, but I don't think they should be included in the table. I guess that Ca10+ in a chemical environment will immediately become Ca2+ if its speed is much less than the speed of light, but Ca is stable, so it can form compounds similar to alkalides? Burzuchius (talk) 12:35, 4 March 2015 (UTC)

Yup, I wouldn't have put in Ca if not for the fact that it was mentioned as stable. Double sharp (talk) 13:20, 5 March 2015 (UTC)

There is an article called A brief introduction to transition metals in unusual oxidation states. Burzuchius (talk) 20:09, 4 March 2015 (UTC)

Plutonium(+8), americium(+8), curium(+8). After the claim of CmO4, there has appeared this article: [28] which seemingly states that Cm(VIII) does not exist. This article seems to state that Pu(VIII) and Am(VIII) do exist but Cm(VIII) and of course Np(VIII) do not. Burzuchius (talk) 20:44, 8 March 2015 (UTC)

Gallium(−2, −4, -5). The paper [29] (in German, p. 72) seems to state that gallium exhibits oxidation states −2, −4, and -5(!) in the magnesium gallides MgGa, Mg2Ga, and Mg5Ga2, respectively. One more article mentioning gallium(−2, −4): [30]. Burzuchius (talk) 21:14, 9 March 2015 (UTC)

Titanium(−1) has been reported not only in bipyridine complexes, but also in some other ones [31], but maybe it is the same error, I don't know.

Ti(−1) exists. I think the article [32], which distinguishes innocent ligands from non-innocent ones, does not mistake. That article also gives an example of Mn(−2), different from the one listed in Greenwood&Earnshaw and Holleman&Wiberg (they list [Mn(phthalocyanine)]2−; is it really [Mn(H2Pc)]2− and not juct [MnPc]2−, which would give Mn(0)?). Burzuchius (talk) 18:24, 3 April 2015 (UTC)

Gold(+4) has been reported, but there is some doubt about its existence, see [33].Burzuchius (talk) 16:21, 27 March 2015 (UTC)

Ruthenium(−1). There is the anion [Ru2CO8]2−, but according to [34], it has an asymmetrical structure, so I wonder whether this ion contains ruthenium(−1) or mixed oxidation states. However, according to [35], the symmetrical anion [Ru2CO8]2− has also been observed. Burzuchius (talk) 21:50, 10 May 2015 (UTC)

Lithium(−1). Ionic lithides are not known, but what about molecular ones? In the gas phase, there exist NaLi [36], KLi [37], RbLi [38], and CsLi [39], the last two having large dipole moments. If the bonds in these compounds are polarized towards Li, then the oxidation state of Li is −1. Is it true that Li is the negative pole in these compounds? (However, in the solid phase under high pressure, Cs is predicted to be anionized: [40]). Burzuchius (talk) 16:39, 21 May 2015 (UTC)

Oxidation states −5 and −6[edit]

I have found a Russian blog listing some examples [41] of oxidation states −5 and −6: BeAlB, Al3BC, Mg5Ga2, Mg5In2, Mg5Tl2, LiMg2Ga; Ca3Zn, Mg3Hg, Ca3Hg, Sr3Hg, Ba3Hg. In other sites, I have found confirmations only for Al3BC ([42], p. 139) and Mg5Ga2 ([43], I have already mentioned it). Burzuchius (talk) 19:09, 10 March 2015 (UTC)

The ion Tl5− has been reported in [44]. However, another ion mentioned in that article, Tl37−, seems to have been disputed in [45].Burzuchius (talk) 11:45, 11 March 2015 (UTC)
[46], p. 15 and [47], p. 5 state that LiMg2Tl is a Zintl phase. If it is so, than the oxidation state of thallium in this compound should be −5.Burzuchius (talk) 11:51, 13 March 2015 (UTC)
A new column, at last! I've been wondering about the negative side for a while! (Unfortunately that will also make it a bit of a pain to insert, but we'll get to it!) Double sharp (talk) 01:11, 14 March 2015 (UTC)
I have added −5. I am not completely sure about the compound of thallium, which is so unusual and non-stoichiometric. Mg5Tl2 and LiMg2Tl have much simpler chemical formulas, but unfortunately I have not found any authoritative source that explicitly stated they have Tl(−5). Burzuchius (talk) 18:24, 3 April 2015 (UTC)
According to [48], LiMg2Tl and Sr5Tl3H do contain Tl(−5).Burzuchius (talk) 21:50, 10 May 2015 (UTC)


The color-coding of elements and noble gases is not in compliance with WP:ACCESSIBILITY. We need a way to indicate that information without having to rely on color.--Jasper Deng (talk) 03:15, 21 July 2015 (UTC)

Things mentioned in the element infoboxes but not here[edit]

Kr(+1), Xe(+1), Ce(+1), Sm(+1, +4), Eu(+1), Dy(+1), Ho(+1), Er(+1), Yb(+1), and Lu(+1) are in their respective infoboxes, but not in this list. Annoyingly none of them are referenced in the infoboxes. Also Au(+4) was in but that's already been questioned above, so I did not hesitate to remove it.

Also, for some reason the Zn infobox mentions 0 explicitly. I wouldn't have expected that to be mentioned explicitly in Zn's case! Now W's infobox gives 0, which makes sense (W(CO)6), but then why not the Cr and Mo analogues? Re, Os, and Ir also give 0; so does Sg, but that makes sense as Sg(CO)6 is known experimentally.

What counts as a common oxidation state? Re(+4) is listed here as its most common state (naturally, this "common" is in the context of Re), but Re(+2, +6, +7) are comparable. This list also bolds things like Kr(+2) and Rn(+2); I didn't in the infoboxes, as this is silly if you show 0 as well for these elements. Double sharp (talk) Double sharp (talk) 10:34, 2 September 2015 (UTC)

As for lanthanides{+1), NIST Chemistry WebBook gives LaH, YbH, LuH, LaF, CeF, NdF, SmF, EuF, GdF, DyF, HoF, ErF, YbF, LuF, PrCl, NdCl, SmCl, EuCl, DyCl, HoCl, and YbCl, and also cyclic (LaH)2, (CeH)2, (PrH)2, (GdH)2, (TbH)2, and (LuH)2 (with 3-centre bonds?). [49] also gives some gaseous diatomic molecules, including LaCl.
As for samarium(+4), NIST gives SmH4. This Russian article also mentions Sm(IV). However, I have not found more information about it.
As for Kr(+1) and Xe(+1): NIST has monohalides, but aren't they exciplexes? See also Xe(+1) above on this talkpage.Burzuchius (talk) 18:09, 5 September 2015 (UTC)

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This supposedly occurs in AcH2, but the actinium article states that its structure is analogous to LaH2. If so it should really be an electride, like LaH2, and would therefore be an actinium(III) compound. Double sharp (talk) 02:03, 6 August 2016 (UTC)

Oxidation State 0[edit]

What I miss in your list is the occurence of diverse elements having oxidation state 0 in compounds. Esp. Metal carbonyls as Fe(CO)5 show the central atom in oxidation state 0. --Heavy Metal Chemist (talk)(german WP) 14:05, 23 September 2016 (UTC)

Fair point. But since it is also automatically present for elements, we need some way of distinguishing trivial cases of oxidation state 0 (such as Be or F2) from interesting cases (such as Fe(CO)5 or Ni(CO)4). I suppose I could amend this to only include oxidation states encountered into compounds, but (1) it's a little arbitrary, since oxidation states are equally defined for single elements, if trivially; and (2) the amount of work that would be needed to add every single possible example to such a list would be somewhat terrifying, given that this list does not restrict itself to common oxidation states, and considers just about everything (including such oddities as NbCl and [IrO4]+) that has been seen in a compound, however unstable (like transient [PoO2]+) to be fair game. Double sharp (talk) 14:42, 23 September 2016 (UTC)
Every single possible example wouldn't be required–one will do. I mention this because I just happened to read in Wiberg that Ca forms compounds in which its oxidation state is apparently zero, such as calcium hexammoniate, Ca(NH3)6. IIRC HOF is an example for oxygen. Sandbh (talk) 09:53, 21 February 2017 (UTC)


The claim of existence of Pu(VIII) is sketchy and not widely accepted; see 10.1021/acs.inorgchem.5b01540 for some theoretical studies. The same is probably true for Am(VIII), which just like Fe(VIII) and Cm(VIII) has not been confirmed by any other group. I am going to remove them. Double sharp (talk) 05:32, 22 November 2016 (UTC)

a surer example of Pu(II)[edit] Double sharp (talk) 15:34, 25 March 2017 (UTC)

Argon - +2?[edit] lists argon as +2.

However, here, it's 0.

What's going on? We need to make these two consistent. (talk) 00:51, 3 April 2017 (UTC)

Argon_compounds#Argon_polyhydrides talks about ArH3+ existing and having a structure that sounds like it could be Ar(II). DMacks (talk) 01:39, 3 April 2017 (UTC)
The status of things like argon compounds and what valence to assign Ar here is complicated by the fact that no one has really determined a value for the Pauling electronegativity of Ar. This makes it a bit difficult to define what exactly the oxidation states in Ar compounds are supposed to be. The 6d transition metals also have this problem, but given that the compounds given here are with clearly nonmetallic elements like O, Cl, and the admittedly more equivocal Se, I think it's not so much in doubt. The trend seems to suggest a value almost as high as that of O for Ar. In the absence of a good source for this I'm inclined to switch the valence table to list argon as 0. Double sharp (talk) 08:55, 3 April 2017 (UTC)
Okay, argon is now 0. There are predictions of Ar(II) in compounds like [ArF]+[AuF6], so we could conceivably change it back at some point. Double sharp (talk) 08:56, 3 April 2017 (UTC)
Sounds reasonable. Always interesting when the "some day someone may well publish something new, and we update accordingly" comes to pass. DMacks (talk) 12:47, 3 April 2017 (UTC)
Personally, in cases where no Pauling electronegativity is available (such as He, Ne, Ar, and the transactinides), my advice would be to substitute the Allen electronegativity, since the latter is available for all elements; in this case, since this method also gives argon an oxidation state of 0 for both of its known compounds (HArF and ArCF22+), I'm agreeing with Double sharp here. Whoop whoop pull up Bitching Betty | Averted crashes 16:53, 4 April 2017 (UTC)
By the way, IUPAC now recommends using Allen electronegativity, not Pauling [50]. Although I see that Allen electronegativity also has some flaws. I think that a better way for constructing a scale of electronegativity would be: first compare the elements (try to construct an electronegativity series for all the elements), and only then assign numbers.Burzuchius (talk) 17:10, 4 April 2017 (UTC)
Holy cow - the IUPAC website specifically mentions the upcoming need to edit the Wikipedia page on electronegativity in order to accommodate forthcoming edits to the Goldbook! Whoop whoop pull up Bitching Betty | Averted crashes 17:17, 4 April 2017 (UTC)

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