List of oxidation states of the elements

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This is a list of known oxidation states of the chemical elements, excluding nonintegral values. The most common states appear in bold. The table is based on that of Greenwood and Earnshaw,[1] with additions noted. Oxidation state 0, which occurs for all elements, is implied by the column with the symbol of the element. The format of the table, which was devised by Mendeleev in 1889, shows the periodicity of the oxidation states of the elements.[1]

List

  Element
  Noble gas
Z Element Negative
oxidation
states
  Positive
oxidation
states
Group Notes
−9−5 −9−4 −9−3 −9−2 −9−1 _0 _+1 _+2 _+3 _+4 _+5 _+6 _+7 _+8 _+9
1 hydrogen −1−1 H +1+1+1 1
2 helium He 18
3 lithium Li +1+1+1 1 [2]
4 beryllium Be +1 +2+2 2 [3]
5 boron −5 −1 B +1 +2 +3+3 13 [4][5]
6 carbon −4−4 −3−3 −2−2 −1−1 C +1+1+1 +2+2 +3+3 +4+4 14
7 nitrogen −3−3 −2 −1 N +1 +2 +3+3 +4 +5+5 15
8 oxygen −2−2 −1 O +1 +2 16
9 fluorine −1−1 F 17
10 neon Ne 18
11 sodium −1 Na +1+1+1 1 [2]
12 magnesium Mg +1 +2+2 2 [6]
13 aluminium −2 −1 Al +1 +2 +3+3 13 [7][8][9]
14 silicon −4−4 −3 −2 −1 Si +1 +2 +3 +4+4 14
15 phosphorus −3−3 −2 −1 P +1 +2 +3+3 +4 +5+5 15
16 sulfur −2−2 −1 S +1 +2+2 +3 +4+4 +5 +6+6 16
17 chlorine −1−1 Cl +1+1+1 +2 +3+3 +4 +5+5 +6 +7+7 17 [10]
18 argon Ar 18
19 potassium −1 K +1+1+1 1 [2]
20 calcium −1 Ca +1 +2+2 2 [11][12]
21 scandium Sc +1 +2 +3+3 3
22 titanium −2 −1 Ti +1 +2 +3 +4+4 4 [13][14][15]
23 vanadium −3 −1 V +1 +2 +3 +4 +5+5 5 [14]
24 chromium −4 −2 −1 Cr +1 +2 +3+3 +4 +5 +6+6 6 [14]
25 manganese −3 −2 −1 Mn +1 +2+2 +3 +4+4 +5 +6 +7+7 7
26 iron −4 −2 −1 Fe +1 +2+2 +3+3 +4 +5 +6+6 8 [16][17]
27 cobalt −3 −1 Co +1 +2+2 +3+3 +4 +5 9 [14]
28 nickel −2 −1 Ni +1 +2+2 +3 +4 10 [18]
29 copper −2 Cu +1 +2+2 +3 +4 11 [17]
30 zinc −2 Zn +1 +2+2 12 [17][19]
31 gallium −5 −4 −2 −1 Ga +1 +2 +3+3 13 [8][20]
32 germanium −4−4 −3 −2 −1 Ge +1 +2+2 +3 +4+4 14 [21]
33 arsenic −3−3 −2 −1 As +1 +2 +3+3 +4 +5+5 15 [8][22][23]
34 selenium −2−2 −1 Se +1 +2+2 +3 +4+4 +5 +6+6 16 [24][25][26][27]
35 bromine −1−1 Br +1+1+1 +3+3 +4 +5+5 +7+7 17
36 krypton Kr +2+2 18
37 rubidium −1 Rb +1+1+1 1 [2]
38 strontium Sr +1 +2+2 2 [28]
39 yttrium Y +1 +2 +3+3 3 [29][30]
40 zirconium −2 Zr +1 +2 +3 +4+4 4 [14][31]
41 niobium −3 −1 Nb +1 +2 +3 +4 +5+5 5 [14][32]
42 molybdenum −4 −2 −1 Mo +1 +2 +3 +4+4 +5 +6+6 6 [14]
43 technetium −3 −1 Tc +1 +2 +3 +4+4 +5 +6 +7+7 7
44 ruthenium −4 −2 Ru +1 +2 +3+3 +4+4 +5 +6 +7 +8 8 [14][17]
45 rhodium −3 −1 Rh +1 +2 +3+3 +4 +5 +6 9 [14]
46 palladium Pd +1 +2+2 +3 +4+4 +5 +6 10 [33][34][35][36]
47 silver −2 −1 Ag +1+1+1 +2 +3 +4 11 [17][37][38]
48 cadmium −2 Cd +1 +2+2 12 [17][39]
49 indium −5 −2 −1 In +1 +2 +3+3 13 [8][40][41]
50 tin −4−4 −3 −2 −1 Sn +1 +2+2 +3 +4+4 14 [8][42][43]
51 antimony −3−3 −2 −1 Sb +1 +2 +3+3 +4 +5+5 15 [8][44][45][46]
52 tellurium −2−2 −1 Te +1 +2+2 +3 +4+4 +5 +6+6 16 [8][47][48][49]
53 iodine −1−1 I +1+1+1 +3+3 +4 +5+5 +6 +7+7 17 [50][51]
54 xenon Xe +2+2 +4+4 +6+6 +8 18 [52]
55 caesium −1 Cs +1+1+1 1 [2]
56 barium Ba +1 +2+2 2 [53]
57 lanthanum La +1 +2 +3+3 [54]
58 cerium Ce +2 +3+3 +4+4
59 praseodymium Pr +2 +3+3 +4
60 neodymium Nd +2 +3+3 +4 [55]
61 promethium Pm +2 +3+3 [56]
62 samarium Sm +2 +3+3
63 europium Eu +2+2 +3+3
64 gadolinium Gd +1 +2 +3+3
65 terbium Tb +1 +2 +3+3 +4 [56]
66 dysprosium Dy +2 +3+3 +4 [57]
67 holmium Ho +2 +3+3 [56]
68 erbium Er +2 +3+3 [56]
69 thulium Tm +2 +3+3
70 ytterbium Yb +2 +3+3
71 lutetium Lu +2 +3+3 3 [56]
72 hafnium −2 Hf +1 +2 +3 +4+4 4 [14][58]
73 tantalum −3 −1 Ta +1 +2 +3 +4 +5+5 5 [14][59]
74 tungsten −4 −2 −1 W +1 +2 +3 +4+4 +5 +6+6 6 [14]
75 rhenium −3 −1 Re +1 +2 +3 +4+4 +5 +6 +7 7
76 osmium −4 −2 −1 Os +1 +2 +3 +4+4 +5 +6 +7 +8 8 [17][60]
77 iridium −3 −1 Ir +1 +2 +3+3 +4+4 +5 +6 +7 +8 +9 9 [61][62][63][64]
78 platinum −3 −2 −1 Pt +1 +2+2 +3 +4+4 +5 +6 10 [17][65][66]
79 gold −3 −2 −1 Au +1 +2 +3+3 +5 11 [17]
80 mercury −2 Hg +1+1+1 +2+2 +4 12 [17][67]
81 thallium −5 −2 −1 Tl +1+1+1 +2 +3+3 13 [8][68][69][70]
82 lead −4 −2 −1 Pb +1 +2+2 +3 +4+4 14 [8][71][72]
83 bismuth −3 −2 −1 Bi +1 +2 +3+3 +4 +5 15 [73][74][75][76]
84 polonium −2−2 Po +2+2 +4+4 +5 +6 16 [77]
85 astatine −1−1 At +1+1+1 +3 +5 +7 17
86 radon Rn +2+2 +6 18 [78][79][80]
87 francium Fr +1+1+1 1
88 radium Ra +2+2 2
89 actinium Ac +2 +3+3 [81]
90 thorium Th +1 +2 +3 +4+4 [82]
91 protactinium Pa +2 +3 +4 +5+5 [83]
92 uranium U +1 +2 +3 +4 +5 +6+6 [84][85]
93 neptunium Np +2 +3 +4 +5+5 +6 +7 [86]
94 plutonium Pu +1 +2 +3 +4+4 +5 +6 +7 +8 [86][87][88]
95 americium Am +2 +3+3 +4 +5 +6 +7 +8 [89][90]
96 curium Cm +2 +3+3 +4 +6 [86][91][92]
97 berkelium Bk +2 +3+3 +4 [93]
98 californium Cf +2 +3+3 +4
99 einsteinium Es +2 +3+3 +4 [94]
100 fermium Fm +2 +3+3
101 mendelevium Md +2 +3+3
102 nobelium No +2+2 +3
103 lawrencium Lr +3+3 3
104 rutherfordium Rf +4+4 4
105 dubnium Db +5+5 5 [95]
106 seaborgium Sg +6+6 6 [96]
107 bohrium Bh +7+7 7 [97]
108 hassium Hs +8+8 8 [98]

A figure with a similar format (shown below) was used by Irving Langmuir in 1919 in one of the early papers about the octet rule.[99] The periodicity of the oxidation states was one of the pieces of evidence that led Langmuir to adopt the rule.

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References and notes

  1. 1.0 1.1 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 27–28. ISBN 0-08-037941-9.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. 2.0 2.1 2.2 2.3 2.4 Na(−1), K(−1), Rb(−1), and Cs(−1) are known in alkalides; the table by Greenwood and Earnshaw shows −1 only for Na and also erroneously for Li; no lithides are described.
  3. Be(I) has been observed in beryllium monohydride (BeH); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  4. B(−1) has been observed in magnesium diboride (MgB2), see James Keeler, Peter Wothers (2014). Chemical Structure and Reactivity: An Integrated Approach. Oxford University Press. <templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  5. B(−5) has been observed in Al3BC, see Melanie Schroeder. "Eigenschaften von borreichen Boriden und Scandium-Aluminium-Oxid-Carbiden" (PDF) (in Deutsch). p. 139.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  6. Low valent magnesium compounds with Mg(I) have been obtained using bulky ligands; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  7. Al(II) has been observed in aluminium(II) oxide (AlO); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value)., and in dialanes (R2Al—AlR2); see Uhl, Werner "Organoelement Compounds Possessing Al—Al, Ga—Ga, In—In, and Tl—Tl Single Bonds" Advances in Organometallic Chemistry Volume 51, 2004, Pages 53–108. doi:10.1016/S0065-3055(03)51002-4
  8. 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 Negative oxidation states of p-block metals (Al, Ga, In, Sn, Tl, Pb, Bi, Po) and metalloids (Si, Ge, As, Sb, Te, At) may occur in Zintl phases, see: [1], p. 259 and [2] (both in German).
  9. Al(−2) has been observed in Sr14[Al4]2[Ge]3, see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  10. The equilibrium Cl2O6⇌2ClO3 is mentioned by Greenwood and Earnshaw, but it has been refuted, see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value)., and Cl2O6 is actually chlorine(V,VII) oxide. However, ClO3 has been observed, see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  11. Ca(I) has been observed; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  12. The Ca ion is known: see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  13. Ti(I) has been observed in titanium monohydride (TiH); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  14. 14.00 14.01 14.02 14.03 14.04 14.05 14.06 14.07 14.08 14.09 14.10 14.11 Ti(−2), V(−3), Cr(−4), Co(−3), Zr(−2), Nb(−3), Mo(−4), Ru(−2), Rh(−3), Hf(−2), Ta(−3), and W(−4) occur in anionic binary metal carbonyls; see [3], p. 4 (in German); [4], pp. 97–100; [5], p. 239
  15. Ti(−1) has been reported in [Ti(bipy)3], but was later shown to be Ti(+3); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value). However, Ti(−1) occurs in [Ti(η-C6H6] and [Ti(η-C6H5CH3)], see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  16. Fe(VII) and Fe(VIII) have been reported; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value). However, their existence has been disputed.
  17. 17.0 17.1 17.2 17.3 17.4 17.5 17.6 17.7 17.8 17.9 Fe(−4), Ru(−4), and Os(−4) have been observed in metal-rich compounds containing octahedral complexes [MIn6−xSnx]; Pt(−3) (as a dimeric anion [Pt–Pt]6−), Cu(−2), Zn(−2), Ag(−2), Cd(−2), Au(−2), and Hg(−2) have been observed (as dimeric and monomeric anions; dimeric ions were initially reported to be [T–T]2− for Zn, Cd, Hg, but later shown to be [T–T]4− for all these elements) in La2Pt2In, La2Cu2In, Ca5Au3, Ca5Ag3, Ca5Hg3, Sr5Cd3, Ca5Zn3(structure (AE2+)5(T–T)4−T2−⋅4e), Yb3Ag2, Ca5Au4, and Ca3Hg2; Au(–3) has been observed in ScAuSn and in other 18-electron half-Heusler compounds. See Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value). and Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  18. Ni(−2) has been observed in Li2[Ni(1,5-COD)2], see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value). and Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  19. Zn(I) has been observed in Zn2Cl2; see Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985). "Zink". Lehrbuch der Anorganischen Chemie (in German) (91–100 ed.). Walter de Gruyter. pp. 1034–1041. ISBN 3-11-007511-3. <templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  20. Ga(−2), Ga(−4), and Ga(−5) have been observed in the magnesium gallides MgGa, Mg2Ga, and Mg5Ga2, respectively; see Patrick Hofmann. "Colture. Ein Programm zur interaktiven Visualisierung von Festkörperstrukturen sowie Synthese, Struktur und Eigenschaften von binären und ternären Alkali- und Erdalkalimetallgalliden" (PDF) (in Deutsch). p. 72.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  21. Ge(−1), Ge(−2), and Ge(−3) have been observed in germanides; see Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1995). "Germanium". Lehrbuch der Anorganischen Chemie (in German) (101 ed.). Walter de Gruyter. pp. 953–959. ISBN 3-11-012641-9. <templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>.
  22. As(I) has been observed in arsenic(I) iodide (AsI); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  23. As(IV) has been observed in arsenic(IV) hydroxide (As(OH)4) and HAsO
    3
    ; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  24. Se(−1) has been observed in diselenides(2−) (Se22−).
  25. Se(I) has been observed in selenium(I) chloride (Se2Cl2); see "Selenium : Selenium(I) chloride compound data". WebElements.com. Retrieved 2007-12-10.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  26. Se(III) has been observed in Se2NBr3; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  27. Se(V) has been observed in SeO2−
    3
    and HSeO2−
    4
    ; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  28. Sr(I) has been observed in strontium monofluoride (SrF); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  29. Y(I) has been observed in yttrium(I) bromide (YBr); see "Yttrium: yttrium(I) bromide compound data". OpenMOPAC.net. Retrieved 2007-12-10.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  30. Y(II) has been observed in [(18-crown-6)K][(C5H4SiMe3)3Y]; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  31. Zr(−1) has been reported in [Zr(bipy)3] (see Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 960. ISBN 0-08-037941-9.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles> and Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1995). "Zirconium". Lehrbuch der Anorganischen Chemie (in German) (101 ed.). Walter de Gruyter. p. 1413. ISBN 3-11-012641-9. <templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>), but was later shown to be Zr(+4); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  32. Nb(I) has been observed in niobium monochloride (NbCl); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  33. Pd(I) has been observed; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  34. Pd(III) has been observed; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  35. Pd(V) has been observed in dioxygenyl hexafluoropalladate; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  36. Pd(VI) complexes have been observed; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  37. The Ag ion has been observed in metal ammonia solutions: see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  38. Ag(IV) has been observed in potassium hexafluoroargentate (K2AgF6) and caesium hexafluoroargentate (Cs2AgF6); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  39. Cd(I) has been observed in cadmium(I) tetrachloroaluminate (Cd2(AlCl4)2); see Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1985). "Cadmium". Lehrbuch der Anorganischen Chemie (in German) (91–100 ed.). Walter de Gruyter. pp. 1056–1057. ISBN 3-11-007511-3. <templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  40. In(–5) has been observed in La3InGe, see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  41. In(−2) has been observed in Na2In, see [6], p. 69.
  42. Sn(−3) has been observed in [Sn2]6−, e.g. in (Ba2)4+(Mg4)8+Sn4−(Sn2)6−Sn2− (with square (Sn2−)n sheets), see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  43. Sn(I) and Sn(III) have been observed in organotin compounds
  44. Sb(−2) has been observed in [Sb2]4−, e.g. in RbBa4[Sb2][Sb][O], see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  45. Sb(I) and Sb(II) have been observed in organoantimony compounds; for Sb(I), see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  46. Sb(IV) has been observed in [SbCl
    6
    ]2−
    , see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  47. Te(I) has been observed in tellurium iodide (TeI), see "Tellurium: tellurium iodide". WebElements.com. Retrieved 2015-02-23.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  48. Te(III) has been observed in [Te(N(SiMe3)2)2]+, see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value)..
  49. Te(V) is mentioned by Greenwood and Earnshaw, but they do not give any example of a Te(V) compound. What was long thought to be ditellurium decafluoride (Te2F10) is actually bis(pentafluorotelluryl) oxide, F5TeOTeF5: see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value). However, Te(V) has been observed in H
    2
    TeO
    4
    , TeO
    3
    , HTeO2−
    4
    , and TeO3−
    4
    ; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  50. I(IV) has been observed in iodine dioxide (IO2); see Pauling, Linus (1988). "Oxygen Compounds of Nonmetallic Elements". General Chemistry (3rd ed.). Dover Publications, Inc. p. 259. ISBN 0-486-65622-5.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  51. I(VI) has been observed in IO3, IO42−, H5IO6, H2IO52−, H4IO62−, and HIO53−; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  52. Xe(I) has been reported in xenon hexafluoroplatinate and xenon hexafluororhodate (see Pauling, Linus (1988). General Chemistry (3rd ed.). Dover Publications, Inc. p. 250. ISBN 0-486-65622-5.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>), however these compounds were later found to contain Xe(II).
  53. Ba(I) has been observed in barium monofluoride (BaF); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  54. La(I) has been observed in lanthanum monohydride (LaH); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  55. Nd(IV) has been observed in unstable solid state compounds; see Holleman, A. F.; Wiberg, E. (2001), Inorganic Chemistry, San Diego: Academic Press, ISBN 0-12-352651-5<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  56. 56.0 56.1 56.2 56.3 56.4 All the lanthanides (La–Lu) in the +2 oxidation state have been observed (except La, Gd, Lu) in dilute, solid solutions of dihalides of these elements in alkaline earth dihalides (see Holleman, A. F.; Wiberg, E. (2001), Inorganic Chemistry, San Diego: Academic Press, ISBN 0-12-352651-5<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>) and (except Pm) in organometallic molecular complexes, see Lanthanides Topple Assumptions and Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).. Additionally, all the lanthanides (La–Lu) form dihydrides (LnH2), dicarbides (LnC2), monosulfides (LnS), monoselenides (LnSe), and monotellurides (LnTe), but for most elements these compounds have Ln3+ ions with electrons delocalized into conduction bands, e. g. Ln3+(H)2(e).
  57. Dy(IV) has been observed in unstable solid state compounds; see Holleman, A. F.; Wiberg, E. (2001), Inorganic Chemistry, San Diego: Academic Press, ISBN 0-12-352651-5<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  58. Hf(I) has been observed in hafnium monobromide (HfBr), see Marek, G.S.; Troyanov, S.I.; Tsirel'nikov, V.I. (1979). "Кристаллическое строение и термодинамические характеристики монобромидов циркония и гафния / Crystal structure and thermodynamic characteristics of monobromides of zirconium and hafnium". Журнал неорганической химии / Russian Journal of Inorganic Chemistry (in русский). 24 (4): 890–893.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  59. Ta(I) occurs in CpTa(CO)4, see Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils (1995). "Tantal". Lehrbuch der Anorganischen Chemie (in German) (101 ed.). Walter de Gruyter. p. 1430. ISBN 3-11-012641-9. <templatestyles src="Module:Citation/CS1/styles.css"></templatestyles> and King, R. Bruce (1969). Transition-Metal Organometallic Chemistry: An Introduction. Academic Press. p. 11. ISBN 0-32-315996-6.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  60. Os(−1) has been observed in Na
    2
    [Os
    4
    (CO)
    13
    ]
    ; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value). and Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  61. Ir(−3) has been observed in Ir(CO)33−; see Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1117. ISBN 0-08-037941-9.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  62. Ir(VII) has been observed in [(η2-O2)IrO2]+; see C&EN: Iridium dressed to the nines.
  63. Ir(VIII) has been observed in iridium tetroxide (IrO4); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  64. Ir(IX) has been observed in IrO+
    4
    ; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  65. Pt(−1) and Pt(−2) have been observed in the barium platinides Ba2Pt and BaPt, respectively: see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  66. Pt(I) and Pt(III) have been observed in bimetallic and polymetallic species; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  67. Hg(IV) has been observed in mercury(IV) fluoride (HgF4); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value)..
  68. Tl(−5) has been observed in Na23K9Tl15.3, see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  69. Tl(−1) has been observed in caesium thallide (CsTl); see King, R. B.; Schleyer, R. (2004). "Theory and concepts in main-group cluster chemistry". In Driess, M.; Nöth, H. Molecular clusters of the main group elements. Wiley-VCH, Chichester. p. 19. ISBN 978-3-527-61437-0.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  70. Tl(+2) has been observed in tetrakis(hypersilyl)dithallium ([(Me3Si)Si]2Tl—Tl[Si(SiMe3)]2), see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value)..
  71. Pb(−2) has been observed in BaPb, see Ferro, Riccardo (2008). Nicholas C. Norman, ed. Intermetallic Chemistry. Elsevier. p. 505. ISBN 978-0-08-044099-6.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles> and Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  72. Pb(+1) and Pb(+3) have been observed in organolead compounds, e.g. hexamethyldiplumbane Pb2(CH3)6; for Pb(I), see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value)..
  73. Bi(−2) and Bi(−1) occur in Zintl phases, e.g. (Ca2+)22[Bi4]4−([Bi2]4−)4[Bi3−]8; see Ponou, Siméon (2006). "Germanides, Germanide-Tungstate Double Salts and Substitution Effects in Zintl Phases". Technische Universität München. Lehrstuhl für Anorganische Chemie mit Schwerpunkt Neue Materialien. p. 68.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  74. Bi(I) has been observed in bismuth monobromide (BiBr) and bismuth monoiodide (BiI); see Godfrey, S. M.; McAuliffe, C. A.; Mackie, A. G.; Pritchard, R. G. (1998). Nicholas C. Norman, ed. Chemistry of arsenic, antimony, and bismuth. Springer. pp. 67–84. ISBN 0-7514-0389-X.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  75. Bi(+2) has been observed in dibismuthines (R2Bi—BiR2), see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  76. Bi(IV) has been observed; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  77. Po(V) has been observed in dioxidopolonium(1+) (PoO+
    2
    ); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  78. Rn(II) has been observed in radon difluoride (RnF2); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value). and Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  79. Rn(IV) is reported by Greenwood and Earnshaw, but is not known to exist; see Sykes, A. G. (1998). "Recent Advances in Noble-Gas Chemistry". Advances in Inorganic Chemistry. 46. Academic Press. pp. 91–93. ISBN 978-0-12-023646-6. Retrieved 22 November 2012.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  80. Rn(VI) is known in radon trioxide (RnO3); see Sykes, A. G. (1998). "Recent Advances in Noble-Gas Chemistry". Advances in Inorganic Chemistry. 46. Academic Press. pp. 91–93. ISBN 978-0-12-023646-6. Retrieved 22 November 2012.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  81. Ac(II) is known in actinium dihydride (AcH2); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  82. Th(I) is known in thorium(I) bromide (ThBr); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  83. Pa(II) is known in protactinium(II) oxide (PaO); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  84. U(I) has been observed in uranium monofluoride (UF) and uranium monochloride (UCl), see Sykes, A. G. (1990). "Compounds of Thorium and Uranium". Advances in Inorganic Chemistry. 34. Academic Press. pp. 87–88. ISBN 0-12-023634-6. Retrieved 22 March 2015.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  85. U(II) has been observed in uranium monoxide (UO), uranium monosulfide (US), uranium acetylide (UC2), and uranium sesquicarbide (U2C3); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  86. 86.0 86.1 86.2 Np(II), Pu(II), Cm(II) have been observed in monoxides (NpO, PuO, CmO) and also in dilute, solid solutions of dihalides of these elements in alkaline earth dihalides; see Holleman, Arnold F. and Wiberg, Nils Textbook of Inorganic Chemistry, pp.1957, 1972, 102 Edition, de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1.
  87. Pu(I) has been observed in plutonium monofluoride (PuF); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  88. Unstable Pu(VIII) complexes can form in alkaline solutions; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  89. Am(VII) has been observed in AmO5−
    6
    ; see Americium, Das Periodensystem der Elemente für den Schulgebrauch (The periodic table of elements for schools) chemie-master.de (in German), Retrieved 28 November 2010 and Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1265. ISBN 0-08-037941-9.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  90. Am(VIII) has been observed; see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  91. Cm(VI) has been observed in curium trioxide (CmO3) and dioxidocurium(2+) (CmO2+
    2
    ); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  92. Cm(VIII) has been reported to possibly occur in curium tetroxide (CmO4); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value). However, new experiments seem to indicate its nonexistence: Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  93. Bk(II) has been observed in berkelium(II) oxide (BkO); see Peterson J. R. and Hobart D. E. "The Chemistry of Berkelium" in Harry Julius Emeléus (Ed.) Advances in inorganic chemistry and radiochemistry, Volume 28, Academic Press, 1984 ISBN 0-12-023628-1, p. 51, doi:10.1016/S0898-8838(08)60204-4
  94. Es(IV) is known in einsteinium(IV) fluoride (EsF4); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  95. Db(V) has been observed in dubnium pentachloride (DbCl5); see H. W. Gäggeler (2007). "Gas Phase Chemistry of Superheavy Elements" (PDF). Paul Scherrer Institute. pp. 26–28.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  96. Sg(VI) has been observed in seaborgium oxide hydroxide (SgO2(OH)2); see Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).
  97. Bh(VII) has been observed in bohrium oxychloride (BhO3Cl); see "Gas chemical investigation of bohrium (Bh, element 107)", Eichler et al., GSI Annual Report 2000. Retrieved on 2008-02-29
  98. Hs(VIII) has been observed in hassium tetroxide (HsO4); see "Chemistry of Hassium" (PDF). Gesellschaft für Schwerionenforschung mbH. 2002. Retrieved 2007-01-31.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  99. Lua error in Module:Citation/CS1/Identifiers at line 47: attempt to index field 'wikibase' (a nil value).

See also