Question

Choose the correct statement(s):
1. Carbon has unique ability to form pπ−pπ multiple bonds with itself .
2. Pb, Sn donot form pπ−pπ multiple bonds.
3. Pb, Sn form pπ−pπ multiple bonds.
4. Carbon can accomodate more than 4 electron.

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

Answer: (A), (B)

2

1. Carbon forms p𝜋-p𝜋 multiple bonds with itself and with other atoms of small size and high electronegativity. for example: $C=C,C\equiv C,C=S,C\equiv N$

2. Heavier elements do not form p𝜋-p𝜋 bonds because their atomic orbitals are too large and diffuse to have effective overlapping.

3. Carbon can accommodate only four pairs of electrons around it, therefore the maximum covalency is four.
Hence option a and c are correct.
THEORY
THEORY
Anomalous behaviour of C:

• Smaller size
• Higher ionization enthalpy
• Higher electronegativity
• Unavailability of d orbitals
• Carbon can accommodate only four pairs of electrons around it, therefore the maximum covalency is four.
• Carbon forms p𝜋-p𝜋 multiple bonds with itself and with other atoms of small size and high electronegativity like C = C, $C\equiv C$, $C\equiv N$, C=S.
• Heavier elements don’t form p𝜋-p𝜋 bonds.
• Their atomic orbitals are too large and diffuse to have effective overlapping.