Question

Which one of these are true/false
(a) $(C{H}_3{)}_{3}N$ is pyramidal in shape while $(Si{H}_3{)}_{3}N$ is planar.
(b) Graphite is a good conductor and diamond is non-conductor.

• A. (a) is true and (b) is false
• B. (a) is false and (b) is true
• C. (a) and (b) are false
• D. (a) and (b) are true

Answer 1

The correct option is D (a) and (b) are true

Option (D) is correct.

$\left(A\right)$ $(C{H}_3{)}_{3}N$ is pyramidal in shape while $(Si{H}_3{)}_{3}N$ is planar.

$(C{H}_3{)}_{3}N$ has $s{p}^3$ hybridization on nitrogen with pyramidal shape due to $p\pi -p\pi$ bonding whereas in $(Si{H}_3{)}_{3}N$, $Si$ has vacant $d$ orbitals which provides $p\pi -d\pi$ bonding and so, nitrogen has $s{p}^2$ hybridization with trigonal planar shape.

$\left(B\right)$ Graphite is a good conductor and diamond is non-conductor.

In diamond, each carbon atom is bonded to $4$ other carbon atoms by $s{p}^3$ bonds, which form a stiff $3-d$ network, which makes it a hard crystal. There are no delocalized electrons and is therefore and insulator.

Graphite on the other hand has each carbon atom bonded to $3$ other carbon atoms by $s{p}^2$ bonds, which gives it a planar structure. Each carbon gives one pair of delocalized electrons. This makes graphite a good conductor of electricity. The planes of graphite are held by weak van der Waals and electronic forces. So, they easily slide over one another. This makes graphite relatively soft.