Question

Evaluate the following statements related to group 14 elements for their correctness.
(A) Covalent radius decreases down the group from C to Pb in a regular manner.
(B) Electronegativity decreases from C to Pb down the group gradually.
(C) Maximum covalence of C is 4 whereas other elements can expand their covalence due to presence of d orbitals.
(D) Heavier elements do not form ppi-ppi bonds.
(E) Carbon can exhibit negative oxidation states.
Choose the correct answer from the options given below:

• A. (C), (D) and (E) Only
• B. (A) and (B) Only
• C. (A), (B) and (C) Only
• D. (C) and (D) Only

Answer 1

The Correct Option is A

Evaluate the following statements regarding Group 14 elements:

1. Statement (A): Covalent radius decreases uniformly from C to Pb down the group.
   Incorrect. Covalent radii generally increase down the group due to added electron shells. However, this increase is irregular, especially in heavier elements like Pb, due to the influence of d and f orbitals.
2. Statement (B): Electronegativity decreases gradually from C to Pb down the group.
   Generally true. Electronegativity tends to decrease with increasing atomic size and shielding effect down the group. However, relativistic effects can cause deviations in elements like Pb.
3. Statement (C): Carbon has a maximum covalence of 4; other Group 14 elements can exceed this due to d orbitals.
   Correct. As a second-period element, carbon lacks d orbitals and is limited to a maximum of four covalent bonds. Heavier elements in Group 14 can utilize their d orbitals to achieve covalence greater than four.
4. Statement (D): Heavier Group 14 elements do not form π-π bonds.
   Correct. Heavier elements (Si, Ge, Sn, Pb) typically do not form stable π-π bonds because their larger atomic size and reduced effective nuclear charge lead to inefficient orbital overlap.
5. Statement (E): Carbon can exhibit negative oxidation states.
   Correct. Carbon can display negative oxidation states, for instance, in carbides (e.g., CaC₂), where its oxidation state is -1.

Evaluation Summary:

• Statement (A) is incorrect; covalent radii increase down the group.
• Statement (B) is largely true but not perfectly gradual due to relativistic effects in heavier elements.
• Statement (C) is correct.
• Statement (D) is correct.
• Statement (E) is correct.

Therefore, the correct statements are (C), (D), and (E) Only.

The correct answer is:

• (C), (D), and (E) Only