Question

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

Fe²⁺

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
Fe2+	6	\[\ce{t^4_{2g}e^2_g}\]

Answer 2

Fe²⁺: 3d⁶

Filling of orbitals in octahedral hydrated ion:

Fe²⁺: \[\ce{t^4_{2g}e^2_g}\]

↑	↑	eg
↑↓	↑	↑	t2g

(4 unpaired electrons)