Question

Which of the following orders is not correct against the given property?

• A. \( Ga<In<Tl<Al<B \) - melting point
• B. \( Al<Ga<In<Tl<B \) - Electronegativity
• C. \( B<Al<Ga<In<Tl \) - Density
• D. \( B<Al<Ga<In<Tl \) - Atomic Radius

Hint:

Atomic size generally increases down a group, but d- and f-electrons can cause irregularities due to poor shielding, affecting the atomic radius trend.

Answer 1

The Correct Option is D

Explanation: - The atomic radius generally increases down a group due to the addition of extra electron shells.
- However, in Group 13, gallium (Ga) has a slightly smaller atomic radius than aluminum (Al) due to the presence of d-electrons, which cause poor shielding, leading to a contraction in size.
- The correct order of atomic radius should be: \( B<Ga<Al<In<Tl \).
- Since the given order contradicts this trend, it is the incorrect one.