Question

Which of the following factors may be regarded as the main cause of lanthanoide contraction?
(a) Greater shielding of 5d electrons by 4f electrons
(b) Poorer shielding of 5d electrons by 4f electrons
(c) Effective shielding of one of 4f electrons by another in the subshell
(d) Poor shielding of one of 4f electron by another in the subshell

Answer 1

Lanthanide contraction is due to poor shielding of one of 4f electron by another in the sub-shell.

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Answer 2

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ANSWER ⤵⤵⤵

(D)

Explanation...

The filling of if orbits before 5d orbits result regular decrease in atomic radii called Lanthanoid contraction or can say the size of radii not much increase.

 In lanthanoid contraction shielding of one 4f electron on another 4f electron is less than shielding of one 5d electron on another 5d electron. 

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