Answer:
0; +1; -1
Explanation:
The resonance structure of HN₃ is shown below (you can also use horizontal dashes to represent the bonding pairs).
The molecule has 16 valence electrons, and each N atom has an octet.
To get the formal charges, cut the covalent bonds in half.
Each atom gets the electrons on its side of the cut.
Formal charge = valence electrons in isolated atom - electrons on bonded atom
FC = VE - BE
(a) On Nₐ
VE = 5
BE = 1 lone pair (2)+ 3 bonding electrons = 2 + 3 = 5
FC = 5 - 5 = 0.
(b) On Nb:
VE = 5
BE = 4 bonding electrons = 4
FC = 5 - 4 = +1
(c) On Nc:
VE = 6
BE = 2 lone pairs(4) + 2 bonding electrons = 4 + 2 = 6
FC = 5 - 6 = -1
