How many of the following metals in +3 oxidation state has number of unpaired electron $\geq 5$ .
Cu, Fe, Mn, Sm, Eu, Gd, Am, Cm, Md, Pu, Np, U, Cf, Lu

Question

How many of the following metals in +3 oxidation state has number of unpaired electron ≥ 5 . Cu, Fe, Mn, Sm, Eu, Gd, Am, Cm, Md, Pu, Np, U, Cf, Lu

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Solution:

We need to determine the number of unpaired electrons for each metal in its +3 oxidation state.

Fe³⁺: [Ar] 3d⁵, 5 unpaired electrons.

Sm³⁺: [Xe] 4f⁵, 5 unpaired electrons.

Eu³⁺: [Xe] 4f⁶, 6 unpaired electrons.

Gd³⁺: [Xe] 4f⁷, 7 unpaired electrons.

Am³⁺: [Rn] 5f⁶, 6 unpaired electrons.

Cm³⁺: [Rn] 5f⁷, 7 unpaired electrons.

Pu³⁺: [Rn] 5f⁵, 5 unpaired electrons.

Cf³⁺: [Rn] 5f⁹, 5 unpaired electrons.

The metals with $\geq 5$ unpaired electrons are Fe, Sm, Eu, Gd, Am, Cm, Pu, Cf. There are 8 such metals.

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