Question

Noble gas compounds like KrF, XeCl, and XeBr are used in excimer lasers. Draw an approximate molecular orbital diagram appropriate for these molecules (they will be quite similar). Give the ground-state electron configuration of KrF and predict whether the cationic analog (KrF) is likely to have a stronger bond.

Answer 1

Here's what I get.

Step-by-step explanation:

The MO diagrams of KrBr, XeCl, and XeBr are shown below.

They are similar, except for the numbering of the valence shell orbitals.

Also, I have drawn the s and p orbitals at the same energy levels for both atoms in the compounds. That is obviously not the case.

However, the MO diagrams are approximately correct.

The ground state electron configuration of KrF is

`(1\sigma_(g))^(2)\, (1\sigma_(u)^(*))^(2) \, (2\sigma_(g))^(2) \, (2\sigma_(u)^(*))^(2) \, (3\sigma_(g))^(2) \,  (1\pi_(u))^(4) \, (1\pi_(g)^(*))^(4) \, (3\sigma_(g)^(*))^(1)`

KrF⁺ will have one less electron than KrF.

You remove the antibonding electron from the highest energy orbital, so the bond order increases.

The KrF bond will be stronger.