Question

Nitrogen in the following compounds N2O3​

Answer 1

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You're answer is here

Answer - The key to this is twofold, the sum of the oxidation numbers for a compound will always be zero, and oxygen almost always has an oxidation number of -2. 

NO --- +2 

NO2 --- +4 

N2O --- +1 

N2O3 --- +3 

N2O5 ---- +5

Answer 2

$\mathfrak{N2O3}$

N O

3 2

Valency of nitrogen is 3

And oxygen is 2