Question

Assign oxidation numbers: N2+3H2=2NH3

Answer 1

First assign an oxidation number to H it's easy because it's always +1 when it's with a nonmetal

Answer 2

\[\rm N_2: \text{The oxidation no. in the elemental state is zero.}\]\[\rm H_2: \text{The oxidation no. in the elemental state is zero.}\]\[\rm NH_3 : \text{The oxidation no. of H is 1+, and so }x + 3\cdot (+1) = 0\]