Selection Rules For UV/vis

Question 1

What are the selection rules for a UV/Vis

Answer 1

Orbital Selection Rule: Quantum number l must change by +/- 1. Therefore allowed: s p or p d

Laporte (Parity Selection rule): allowed: g->u. Forbidden: u->u or g->u

Spin Selection Rule: Electron spin must not be changed when promoted by hv

Question 2

Why are some colours deeper than others sometimes? (Think of ligands and d0 complexes)

Answer 2

This is because there is movement of electrons between a ligand based orbital to a metal based orbital.

You may also have metal based to orbital based, where metal electrons go into the pi* orbitals of the pi-acceptor ligands.

Question 3

Number of d-d transitions?

Answer 3

0 1 3 3 1 0 1 3 3 1 0