Question

Which of the following statement is correct?
I) Atomic radius of Na is greater than that of Mg.
II) Metallic bond in Mg is stronger than the metallic bond in Na.
III) Melting and boiling points of Mg are greater than that of Ca.
IV) Mg and Ca are most abundant elements among the alkaline earth metals.

• A. III, IV
• B. I, II, IV
• C. II, IV
• D. I, IV

Answer 1

The correct option is B I, II, IV

The nuclear charge of sodium is lower than the nuclear charge of magnesium. Hence, the atomic radius of sodium is greater than that of magnesium.
Due to greater nuclear charge of $Mg$ than that of $Na$, the attraction of nucleus for outermost electron is stronger for $Mg$ than for $Na$. Hence, the metallic bond in $Mg$ is stronger than that of $Na$.
Magnesium has lower melting and boiling points than that of $Ca$. This is due to higher effective nuclear charge on $Ca$ than $Mg$ which leads to stronger bonds.
Among the alkaline earth metals, $Mg$ and $Ca$ have highest abundance.