Question

Which one of the following pairs of elements has the second element with greater first ionization energy?

• A. Be and B
• B. Mg and Ca
• C. Al and Ga
• D. Si and Ge

Answer 1

The correct option is C Al and Ga

(I.E)Ga > (I.E) Al
$\to$ This is because of the poor shielding of $d-e^{-}$. (d-orbital contraction)
$I.E{)}_{Be}>{I.E}_B$ (more penetration of 2s electrons)
$I.E{)}_{Mg}>{I.E}_{Ca}$ (size of Ca is more than that of Mg)
$(IE{)}_{si}>(IE{)}_{Ge}$ (size of Ge is more than that of Si)