Name the following anions 1. O 2. N^-13 3. Br^-1?

1. It should be O^-2, oxide ion.

2. It should be N^-3, nitride ion. (Note that azide ion is N3^-1 instead).

3. It is Br^-1, bromide ion.

As KennyB said, If you have O^2-, that is an oxide ion. O2 is simply oxygen, and isn't an anion.

N^3- is nitride (not azide). (As you have written it, N^-13 isn't anything.

Br^- is bromide.

Number three is bromide
Number one is not an anion. If it was O-2, it would be oxide
Number two is non-existent. If it was N-3 it would be azide