Oxidation states of the first transition series
The positive oxidation states of scandium to zinc, with their d-electron counts, how common they are and a representative species.
| 3 | 0 | most stable | scandium oxide (white) | ||
| 2 | 2 | rare | titanium monoxide (black) | ||
| 3 | 1 | common | hexaaquatitanium(III) (violet) | ||
| 4 | 0 | most stable | titanium dioxide (white pigment) | ||
| 2 | 3 | common | vanadium(II) (violet, strong reductant) | ||
| 3 | 2 | common | vanadium(III) (green) | ||
| 4 | 1 | most stable | vanadyl, oxovanadium(IV) (blue) | ||
| 5 | 0 | common | dioxovanadium(V) (yellow); V₂O₅ catalyses the contact process | ||
| 2 | 4 | common | chromium(II) (sky blue, easily oxidised) | ||
| 3 | 3 | most stable | chromium(III); Cr₂O₃ is a green pigment | ||
| 4 | 2 | rare | chromium dioxide (magnetic tape) | ||
| 5 | 1 | rare | chromate(V) (a few compounds only) | ||
| 6 | 0 | common | dichromate (orange, strong oxidant) | ||
| 2 | 5 | most stable | manganese(II) (very pale pink) | ||
| 3 | 4 | common | manganese(III) oxide; Mn³⁺ disproportionates in water | ||
| 4 | 3 | common | manganese dioxide (black-brown; battery cathodes) | ||
| 5 | 2 | rare | manganate(V) (blue, very unstable) | ||
| 6 | 1 | common | manganate(VI) (green, stable only in base) | ||
| 7 | 0 | common | permanganate (purple, strong oxidant) | ||
| 2 | 6 | common | iron(II) (pale green, oxidised by air) | ||
| 3 | 5 | most stable | iron(III); rust is Fe₂O₃·xH₂O | ||
| 4 | 4 | rare | ferryl species (enzyme intermediates) | ||
| 6 | 2 | rare | ferrate(VI) (red-purple, very strong oxidant) | ||
| 2 | 7 | most stable | cobalt(II) (pink) | ||
| 3 | 6 | common | cobalt(III), stable in complexes (orange-yellow) | ||
| 4 | 5 | rare | partly Co(IV) in a charged LiCoO₂ battery cathode | ||
| 2 | 8 | most stable | nickel(II) (green) | ||
| 3 | 7 | rare | nickel oxyhydroxide (NiMH battery electrode) | ||
| 4 | 6 | rare | a few compounds only | ||
| 1 | 10 | common | copper(I) oxide (red); Cu⁺ disproportionates in water | ||
| 2 | 9 | most stable | copper(II) (light blue) | ||
| 3 | 8 | rare | a few compounds only | ||
| 2 | 10 | most stable | zinc ion (colourless) |
Only positive states are listed; 0 and negative states occur in carbonyls and similar complexes. “Most stable” means the state most often met in water with air present. d count = group number − oxidation state.