Question

Which of the following molecules has highest bond dissociation enthalpy?

• A. \(\text{Cl}_{2}\)
• B. \(\text{F}_{2}\)
• C. \(\text{Br}_{2}\)
• D. \(\text{I}_{2}\)

Hint:

The F-F bond is unusually weak because of lone pair repulsion in the small fluorine atom.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
Bond dissociation enthalpy generally decreases down a group as atoms get larger, but fluorine is an exception.

Step 2: Fluorine anomaly
In \(\text{F}_2\) the atoms are very small and the lone pairs on the two atoms repel strongly, which weakens the bond.

Step 3: Known order
\(\text{Cl}_2>\text{Br}_2>\text{F}_2>\text{I}_2\) in bond dissociation enthalpy.

Final Answer:
Chlorine has the highest bond dissociation enthalpy. \[ \boxed{\text{(A) }\text{Cl}_{2}} \]