Question

Explain actinoid contraction.

Answer 1

Actinoid contraction refers to the gradual decrease in the ionic radii with increase in atomic number of actinoids. $5f$ electrons improperly shield one another. In the actinoid series, the nuclear charge and number of $5f$electrons increases by one unit. But due to imperfect shielding of $5f$ orbitals the effective nuclear charge increases and causes contraction is size.