Questions

NH3, Ammonia is a neutral compound as the individual oxidation numbers elements that make up the compound NH3 are Nitrogen (N) and Hydrogen (H) sum to zero. 

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.

Here the oxidation number of Nirogen is -3 and that of Hydrogen is +1.

Now, NH3 = 1(-3) + 3(+1) = -3 + 3 = 0.

The sentence is grammatically and contextually correct. This is because, the verb, ‘to look forward to’ means toanticipate. It requires a direct object and it will be the gerund form of the verb i.e. ‘meeting’. Thus, the correct formation would be, ‘My brother is looking forward to meeting his employer tomorrow’.