MHT CET 2026 Chemistry question

Which of the following factors may be regarded as the main cause of lanthanide contraction?

(A)Poor shielding of one of 4f electron by another in the sub-shell.Correct
(B)Effective shielding of one of 4f electrons by another in the subshell
(C)Poorer shielding of 5d electrons by 4f electrons
(D)Greater shielding of 5d electrons by 4f electrons

Answer: (A)

Solution

Across the lanthanoids (Ce to Lu) the nuclear charge increases by one at each step and the additional electron enters the inner 4f subshell. The f orbitals have diffuse shapes, so one 4f electron shields another 4f electron only very poorly from the increased nuclear charge. The effective nuclear charge felt by the

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Question ID VK-098635