The Molecular orbitals of the Cyanide anion

The display shows the five occupied valence molecular orbitals and three unoccupied orbitals. The Calculation was done at the following level: B3LYP/6-31G(d). A tutorial on how to construct the diagram from the starting atomic orbitals.

Note in particular the odd form of the 6σ antibonding orbital. Being anti-bonding, it is supposed conventionally to have a node along the C-N bond. In fact, the node instead occurs in a cone surrounding the bond rather than lying along it!

3D rotatable modelEnergy in Hartree
6σ 0.59224
2π 0.35633 2π 0.35633

5σ 0.01886
1π -0.01779 1π -0.01779
4σ -0.10521
3σ -0.56364

H. S. Rzepa, October 2007