what are the half reactions for

Question

a) Cr(NO3)2
b) Pb(NO3)2

I know that Cr and Pb are:
Cr^2+ +2e- -> Cr
Pb^2+ +2e- -> Pb

I just don't know how to do the half reaction for (NO3)2

Answer 1

I believe NO3^- is just a spectator ion.