Question

Reason of lanthanoid contraction is:-
(a) Negligible screening effect of ‘f ’ orbitals
(b) Increasing nuclear charge
(c) Decreasing nuclear charge
(d) Decreasing screening effect

Answer 1

negligible effect of f orbitals

Answer 2

hi friend.....

your correct option is (a) Negligible screening effect of ‘f ’ orbitals.

explanation....

Lanthanoid contraction is the regular decrease in atomic and ionic radii of lanthanides. This is due to the imperfect shielding or poor screening effect of orbitals due to their diffused shape, which unable to counterbalance the effect of the increased nuclear charge. Hence, the net result is a contraction in size of lanthanoids.

hope i answered your question.....