Question

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

Co²⁺

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
Co2+	7	\[\ce{t^5_{2g}e^2_g}\]

Answer 2

Co²⁺: 3d⁷

Filling of orbitals in octahedral hydrated ion:

Co²⁺: \[\ce{t^5_{2g}e^2_g}\]

↑	↑	eg
↑↓	↑↓	↑	t2g

(3 unpaired electrons)