With the help of molecular orbital theory we can easily calculate the bond energy and bond length of both CN and CN – species. The basic thing we need to calculate is the electronic Configuration of CN.
Total no of electrons in CN are 13. i.e.So, the EC of CN is :
CN: KK σ (2s)2 σ*(2s)2π (2py)2σ (2pz)1
Bond order = [number of bonding electrons – number of anti-bonding electrons]/ 2
So the bond order will become :
Hence, Bond order = 1/2(7–2) =2.5
If we consider the electronic configuration of CN – then one electron will shift to σ(2pz) 1
After the electron shifting the electronic configuration will be
CN-: KKσ(2s)2σ*(2s)2π(2py)2σ (2pz)2
So, bond order = 1/2 (8–2) = 3
From the above discussion it is clear that CN- is having the higher value of bond order. Bond energy is in direct proportion to bond order. As the bond order will increase bond energy will also increase. So CN- will have high bond order and bond energy than CN+. But the bond length of CN- will be less as compared to CN+.