Chromium oxide

Chromium oxide can refer to any of these compounds:

Chromium(II) oxide, basic, reducing agent, black
Chromium(III) oxide, basic, unreactive, green
Chromium(IV) oxide, black, crystalline, hard to make
Chromium(VI) oxide, acidic, strong oxidizing agent, red, toxic

Related pages
Chromic acid, a mixture of chromium(VI) oxide and water