Answer
(a) cobalt (II) oxide
(b) cobalt (III) oxide
(c) cobalt (IV) oxide
Work Step by Step
(a) cobalt (II) oxide
Cobalt (II) means that this cobalt atom has a valence of 2+. Oxygen has a valence of 2-. Therefore, the two elements combine in a one-to-one ratio.
(b) cobalt (III) oxide
Copper (III) means that this cobalt atom has a valence of 3+. Oxygen has a valence of 2-. Therefore, in order for the charges in the compound to be balanced, we need two cobalt atoms for every three oxygen atoms.
(c) cobalt (IV) oxide
Copper (IV) means that this copper atom has a valence of 4+. Oxygen has a valence of 2-. This is a ratio of 1:2. Therefore, in order for the charges in the compound to be balanced, we need one cobalt atom for every two oxygen atoms.
