Lanthanoid contraction is caused due to:

Options

A. the same effective nuclear charge from Ce to Lu
B. the imperfect shielding on outer electrons by 4f electrons from the nuclear charge
C. the appreciable shielding on outer electrons by 4f electrons from the nuclear charge
D. the appreciable shielding on outer electrons by 5d electrons from the nuclear charge

Answer

B

Explanation

The imperfect shielding on outer electrons by 4f electrons from the nuclear charge