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Question

Chemistry Question on d -and f -Block Elements

The electronic configuration of gadolinium (at. no. = 64) is

A

[Xe]4f35d56s2[ Xe ] 4 f ^{3} 5 d ^{5} 6 s ^{2}

B

[Xe]4f65d26d2[ Xe ] 4 f ^{6} 5 d ^{2} 6 d ^{2}

C

[Xe]4f85d96s2[ Xe ] 4 f ^{8} 5 d ^{9} 6 s ^{2}

D

[Xe]4f75d16s2[ Xe ] 4 f ^{7} 5 d ^{1} 6 s ^{2}

Answer

[Xe]4f75d16s2[ Xe ] 4 f ^{7} 5 d ^{1} 6 s ^{2}

Explanation

Solution

The electronic configuration of La(Z=57)La ( Z = 5 7 ) is [Xe]5d16s2[ Xe ] 5 d ^{1} 6 s ^{2}. Therefore, further addition of electrons occurs in a lower energy 4f4 f -orbital till it is exactly half filled at Eu(Z=63)\operatorname{Eu}( Z = 6 3 ). Thus, the electronic configuration of Eu is [Xe]4f76s2.[ Xe ] 4 f ^{7} 6 s ^{2} . Therefore, addition of next electron doesn't occur in a more stable exactly half-filled 4f74 f ^{7} shell but occur in a little higher energy 5d-orbital. Thus, the electronic configuration of Gd(Z=64)Gd ( Z =64) is [Xe]4f75d16s2[ Xe ] 4 f ^{7} 5 d ^{1} 6 s ^{2}