Ques. 1AIPMT 2000
Right order of dissociation energy N2 and N2+ is
- N2 > N2+
- N2 = N2+
- N2+ > N2
- none
Answer
(1) N2 > N2+
Solution
As per NCERT (MO theory), N2 (14 electrons) has the configuration
1s2 *1s2 2s2 *2s2 ( 2px2 = 2py2) 2pz2
so its bond order = 10 - 42 = 3.
In N2+ (13 electrons) one electron is removed from the bonding 2pz orbital, so its bond order = 9 - 42 = 2.5.
A higher bond order means a stronger bond and hence a higher dissociation energy.
∴ N2 > N2+
Answer: (1)