Question

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

• A. If both assertion and reason are true and reason is the correct explanation of assertion
• B. If both assertion and reason are true but reason is not the correct explanation of assertion
• C. If assertion is true but reason is false
• D. If both assertion and reason are false

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