What is the total number of oxygen atoms on the right-hand side of this chemical equation?

The chemical equation is

Cu(s) +4HNO3(aq) ⇒ Cu(NO3)2(aq) + 2NO2(g) + 2H2O(g)

12

Explanation:

In the right hand side of the equation, there are three compound which contains O2, which are;

Cu(NO3)2 , number of oxygen atoms =3*2 =6

2NO2, number of oxygen atoms = 2*2=4

2H2O, number of oxygen atoms =2*1=2

Total number of oxygen atoms on the right side of equation = 6+4+2 =12

it is stable as it is in group 0 which have full outer shells of electrons