Question

Use molecular orbital theory to predict reasonable first excited configurations for C2 and N2. Determine and order the term symbols for each configuration. Use the notation σg1s, etc. for the orbitals and the notation 1Σg etc, for the terms.

Answer 1

First excited configurations for C2

Using the correlation diagram, the electron configuration of C2 is

(1 σ g )²(1 σ u* )²(2 σ g )² (2 σ u* )²(1π u)⁴ .

The bond order of C2 is

          Bond order                =                   Bonding electrons - Antibonding electrons

                      2

                                            =                                 8 - 4

                                                                                   2

BondOrder =    2.

First excited configurations for N2

Using the correlation diagram, the electron configuration of N2 is

(1σ g )² ( 1σ u * )² (2σ g )² (2σ u * )² (1π u)⁴ (3 σg )²

.

The bond order is

               Bond order   =          Bonding electrons - Antibonding electrons

                                                                       2

                                                 =                           10 - 4

                                                                                  2

BondOrder = 3.