Question

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

Fe³⁺

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
Fe3+	5	\[\ce{t^3_{2g}e^2_g}\]

Answer 2

Fe³⁺: 3d⁵

Filling of orbitals in octahedral hydrated ion:

Fe³⁺: \[\ce{t^3_{2g}e^2_g}\]

↑	↑	eg
↑	↑	↑	t2g

(5 unpaired electrons)