Question

What is the electronic configuration of the first row transition metals and their dications? Why is the configuration of `Cr^(2+)` unusual?

Answer 1

From the `4s` subshell........`a.`

Explanation:

The atomic configuration of the first row transition series is....:

`1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(2)3d^n`

The ionic configuration of the `M^(2+)` cation is (usually)........

`[1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^n]^(2+)`

The `4s` electrons are conceived to be removed FIRST upon ionization. And for the explanation, you will have to consult your text. Note that the `3d` and `4s` electrons are very close in energy, and their relative energies may change upon ionization.

`Cr^(2+)` is a notable exception in that its `3d^(5)4s^1` possesses maximum multiplicity with respect to spin quantum number. Anyway, please consult your text.