Question

What is the oxidation number of ammonia (NH3)?

Answer 1

We do not speak of the oxidation number of a molecule. We can speak of the oxidation numbers of the individual elements that make up the compound.

Explanation:

The sum of the oxidation numbers is the charge on the ion or molecule. Because ammonia is neutral, the individual oxidation numbers must sum to zero.

Since the oxidation number of hydrogen is generally `+I`, and it is here, the oxidation number of nitrogen in ammonia is `-III`. When ammonia is synthesized, we speak of dinitrogen reduction in that the oxidation number of nitrogen is reduced from `0` to `-III`.

i.e.......

`1/2stackrel(0)N_2+3/2stackrel(0)H_2rarrstackrel(""^(-III))Nstackrel(""^(+I))H_3`