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

Correct option (a) negligible screening effect of 'f' -orbitals

Explanation :

Due to poor shielding effect of 4f orbitals, nucleus will exert a strong attraction and size of atom or ion goes on decreasing as move in the series with increase in atomic number.