The dand fblock elements - Result Question 8
####8. Reason of lanthanoid contraction is:-
[2014]
(a) Negligible screening effect of ’ $f$ ’ orbitals
(b) Increasing nuclear charge
(c) Decreasing nuclear charge
(d) Decreasing screening effect
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Solution:
- (a) The shape of $f$-orbitals is very much diffused and they have poor shielding effect.
The effective nuclear charge increases due to imperfect shielding of one electron by another in the same subshell which causes the contraction in the size of electron charge cloud. This contraction in size is known as lanthanoid contraction.
