Question

Write down the number of 3d electrons in the following ion:

Cr³⁺

Indicate how would you expect the five 3d orbitals to be occupied for this hydrated ions (octahedral).

Answer 1

Metal ion	Number of d-electrons	Filling of d-orbitals
Cr3+	3	\[\ce{t^3_{2g}}\]

Answer 2

Cr³⁺: 3d³

Filling of orbitals in an octahedral hydrated ion:

Cr³⁺: \[\ce{t^3_{2g}}\]

		eg
↑	↑	↑	t2g

(3 unpaired electrons)