Question

Assertion : Atomic radius of Ga is larger than that of aluminium.
Reason: Atomic radius always increases down the group.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is D Both Assertion and Reason are incorrect

• The atomic radius of the Ga is less than Al because of poor screening effect. The atomic radius of Ga is slightly lesser than of Al because in going from Al to Ga, the electrons have already occupied 3d sub shell in Ga.
  
• The number of energy levels increases as you move down a group as the number of electrons increases. Each subsequent energy level is further from the nucleus than the last. Therefore, the atomic radius increases as the group and energy levels increase.
  
• It is not necessary that atomic radius should always increase down the group as the example is mentioned above even $Ga$ is below $Al$ but has lower atomic radius.
• Hence, both the Assertion and Reason are incorrect.