Question

Which of the following relation is correct with respect to first (I) and second (II) ionization energies of sodium and magnesium ?

• A. $I_{Mg}=I{I}_{Na}$
• B. $I_{Na}>I_{Mg}$
• C. $I{I}_{Mg}>I{I}_{Na}$
• D. $I{I}_{Na}>I{I}_{Mg}$

Answer 1

The correct option is D $I{I}_{Na}>I{I}_{Mg}$

Na has electronic configuration as $1s^{2}2s^{2}2p^{6}3s^1$ while Mg has electronic configuration as $1s^{2}2s^{2}2p^{6}3s^2$. Mg has full filled 3s orbital and Na has 3s half filled so removal an electron will be difficult in case of Mg so first ionization energy of Mg is higher.

now for second ionization electron is being removed from full filled 2p orbital of Na and half filled 3s orbital of Mg. Since 2p is more closer to nucleus and it is full filled too so it require more energy to remove an electron. Hence sond ionization energy of Na is higher than that of Mg