Question

Assertion : The heavier p-block elements do not form strong $\pi$ bonds.
Reason : The heavier elements of p-block form $d\pi -d\pi$ bonds.

• A. Both A and R are true and R is the correct explanation of A.
• B. A is true but R is false.
• C. A is false but R is true.
• D. Both A and R are true but R is not the correct explanation of A.

Answer 1

Answer: (A)

The presence of the d-orbitals influences the chemistry of the heavier elements in a number of other ways. The combined effect of size and availability of d orbitals considerably influences the ability of these elements to form π bonds.

The heavier elements do form π bonds but this involves d orbitals (dπ – pπ or dπ –dπ ). As the d orbitals are of higher energy than the p orbitals, they contribute less to the overall stability of molecules than does pπ - pπ bonding of the second row elements.

Option A is correct.