The oxidation numbers of nitrogen in NH3, HNO3, and NO2 are, respectively:

A) - 3, - 5, + 4

B) + 3, + 5, + 4

C) - 3, + 5, - 4

D) - 3, + 5, + 4

is it D?

The sum of all the charges of individual atoms sum up to the net charge of the compound / ion.

In NH₃, overall its a neutral compound, net charge = 0

oxidation number of N + 3 (oxidation state of H) = 0

charge of H is - 1

oxidation number of N + 3 (-1) = 0

N - 3 = 0

Oxidation number of N = + 3

In HNO₃

oxidation number of O = - 2

oxidation number of H = + 1

H + N + 3 (O) = 0

1 + N + 3 (-2) = 0

N = + 5

in NO₂,

oxidation number of N + 2 (oxidation number of O) = 0

oxidation number of O = - 2

N + 2 (-2) = 0

N = + 4

oxidation number of N = 4

answer is

B) + 3, + 5, + 4