Question

What is the number of oxygen atoms bonded to chlorine in its strongest oxoacid?

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

Oxoacid strength rule: More Oxygen Atoms $\rightarrow$ Higher Oxidation State $\rightarrow$ Stronger Acid! For chlorine: $\text{HClO} < \text{HClO}_2 < \text{HClO}_3 < \text{HClO}_4$.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
We must identify the strongest oxoacid of chlorine and count the number of oxygen atoms bonded to the central chlorine atom within that molecule.

Step 2: Detailed Explanation:
Chlorine forms a series of four primary oxoacids:
1. Hypochlorous acid ($\text{HClO}$): Oxidation state of Cl is +1.
2. Chlorous acid ($\text{HClO}_2$): Oxidation state of Cl is +3.
3. Chloric acid ($\text{HClO}_3$): Oxidation state of Cl is +5.
4. Perchloric acid ($\text{HClO}_4$): Oxidation state of Cl is +7.
Acid strength for a series of oxoacids containing the same central atom increases directly with the oxidation state of that central atom. As the oxidation state increases, the central atom pulls more electron density away from the O-H bond, making it easier to release the $\text{H}^+$ ion. Additionally, the resulting conjugate base ($\text{ClO}_4^-$) is highly stabilized by resonance across four highly electronegative oxygen atoms.
Therefore, the strongest oxoacid of chlorine is perchloric acid ($\text{HClO}_4$).
Looking at the chemical formula $\text{HClO}_4$, there are exactly 4 oxygen atoms bonded to the central chlorine atom.

Step 3: Final Answer:
The number of oxygen atoms is 4, matching option (d).