Question

Which of the following statements regarding Pi \((π)\) bond is NOT true ?

• A. It is weaker than sigma bond.
• B. It is formed by lateral overlapping of two half filled P orbitals.
• C. It is formed after the formation of sigma bond.
• D. The presence of Pi \((π)\) bond increases the bond length of covalent bond.

Hint:

A pi bond adds to bonding between two atoms, so it pulls them closer.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
A pi (\(\pi\)) bond forms when two half filled p orbitals overlap sideways (laterally). It always forms after a sigma bond has already been formed along the internuclear axis.

Step 2: Check statement (A):
Lateral overlap is less effective than head-on overlap, so the pi bond is weaker than the sigma bond. (A) is TRUE.

Step 3: Check statements (B) and (C):
Pi bonds form by lateral overlap of two half filled p orbitals, so (B) is TRUE. The sigma bond forms first and the pi bond follows, so (C) is TRUE.

Step 4: Check statement (D):
Adding a pi bond between two atoms increases the electron density between the nuclei and pulls them closer. For example, carbon-carbon bond length falls from 154 pm (single) to 134 pm (double) to 120 pm (triple). So the pi bond decreases the bond length and (D) is NOT true.

Final Answer:
The statement that is not true is (D). \[ \boxed{\text{(D)}} \]