How would you explain the lower atomic radii of `Ga` as compared to `Al`?

Options

A. poor screening effect of d-electrons for the outer electrons from increased nuclear charge
B. increased force of attraction of increased nuclear charge on electrons
C. increased ionisation enthalpy of Ga as compared to Al
D. anomalous behaviour of Ga.

Answer

A

Explanation

Presence of 10 d-electrons in gallium which have poor screening effect on the outer electrons increases the force of attraction between the outermost electrons and nuclear charge resulting in decreases in atomic radius.