Topic: Atomic and ionic radii· Classification of Elements and Periodicity in Properties

The correct order of atomic radii in group 13 elements is

1. B < Al < In < Ga < Tl

2. B < Ga < Al < Tl < In

3. B < Al < Ga < In < Tl

4. B < Ga < Al < In < Tl

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Answer: 4. B < Ga < Al < In < Tl

Atomic radius generally increases down a group, but Ga is smaller than Al.

Gallium follows the d-block (3d) elements, whose poor shielding raises the effective nuclear charge, so Ga (135 pm) is slightly smaller than Al (143 pm). The order is B (85) < Ga (135) < Al (143) < In (167) < Tl (170).

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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The correct order of atomic radii in group 13 elements is

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