Question

Given below are two statements :
Statement I: In group 13, the stability of +1 oxidation state increases down the group.
Statement II: The atomic size of gallium is greater than that of aluminium. In the light of the above statements.
Choose the most appropriate answer from the options given below:

• A. Statement I is incorrect but Statement II is correct
• B. Both Statement I and Statement II are correct
• C. Both Statement I and Statement II are incorrect
• D. Statement I is correct but Statement II is incorrect

Answer 1

The Correct Option is D

Statement I: Number of d and f electrons increases down the group and due to poor shielding of d and f electrons, stability of lower oxidation states increases down the group.

Statement II: The atomic size of aluminium is greater than that of gallium. Thus, Statement I is correct, but Statement II is incorrect.

Answer 2

Step 1: Examine Statement I
Statement I: “In group 13, the stability of +1 oxidation state increases down the group.”

In group 13 (B, Al, Ga, In, Tl), the inert pair effect becomes more prominent as we move down the group. This effect causes the two s-electrons to remain paired and less available for bonding, stabilizing the +1 oxidation state for heavier elements like thallium (Tl).

✔ Therefore, the +1 oxidation state becomes more stable down the group.
Hence, Statement I is correct.

Step 2: Examine Statement II
Statement II: “The atomic size of gallium is greater than that of aluminium.”

Although gallium comes after aluminium in the periodic table, its atomic radius is slightly smaller than expected because of the poor shielding effect of the 3d electrons present in gallium. These 3d electrons do not shield the outer electrons effectively, resulting in increased effective nuclear charge and smaller atomic size.

✖ Therefore, gallium’s atomic size is actually slightly less than that of aluminium.
Hence, Statement II is incorrect.

Step 3: Final conclusion

Statement I is correct but Statement II is incorrect