Question

The first ionization polential of Na, Mg, Al and Si are in the order

a) Na < Mg > Al < Si

b) Na > Mg > Al > Si

c) Na < Mg > Al < Si

d) Na > Mg > Al > Si

Answer 1

Correct option is d) Na > Mg > Al > Si

Across the period the ionization potential increases as the electron enters the same shell so the effective nuclear charge increases thus the order for Na, Al, Si is Na < Al < Si but Mg has the maximum ionization potential because its configuration is 1s² 2s² 2p⁶ 3s² i.e. completely filled 3s subshell thus more stable have the order is Na < Mg > Al > Si