Question

How does the bond length vary in dicarbon species C2,C2-,C22-

Answer 1

Answer:

Bond order is inversely proportional to bond length

Explanation:

First  to find the bond order two methods can be followed

1. From lewis dot structures

2. From MOT

Molecular orbital theory is more preferred in case of diatomic species

MOT of C2 - pi orbitals first filled and then sigma2pz orbital is filled  

12 electrons need to be filled as it is a diatomic molecule (6+6)

Bond order = 1/2(Number of electrons in bonding orbitals - Number of electrons in antibonding orbitals)

=1/2(8-4) = 2

MOT of C2-

So one electron is added i.e., (6+6+1) = 13

Hence the bond order = 1/2(9-4) = 2.5

MOT of C22-

Total of 14 electrons

Bond order = 1/2 (10-4) = 3

Since bond order is inversely proportional to bond length the order will be

C2>C2->C22-