AHL Extension3.1.5

The Transition Elements

Atom: [ A r ] 3 d 10 4 s 2 [Ar]3d^{10}4s^2 [ A r ] 3 d 10 4 s 2 (Full)
Ion (Zn²⁺): [ A r ] 3 d 10 [Ar]3d^{10} [ A r ] 3 d 10 (Full)

Defining the d-block: Why Zinc doesn't make the cut.

1. The Strict IUPAC Definition

"An element whose atom has a partially filled d-subshell, or which can give rise to cations with an incomplete d-subshell."

NOT a transition metal.

Result: Colorless, Diamagnetic.

IS a transition metal.

Note: Its only ion $Sc^{3+}$ is empty ( $3d^0$ ), so its compounds are clear.

The 4s and 3d energies are very close. Electrons can be removed from both without huge energy jumps.
Example: $Fe^{2+}$ and $Fe^{3+}$ .