Group 17 Elements

Halogens in general are very reactive due to high electro negativity, high electron affinity and compartively low bond energies.
The reactivity of halogens decreases with increase in atomic number. The correct order of reactivity of halogens is

Step 1: Understand the bonding in oxyacids of chlorine.
In oxyacids of chlorine, such as chloric acid ( ), the Cl–O bond involves both sigma and pi bonding. The sigma bond is formed by the overlap of orbitals along the internuclear axis, while the pi bond involves the sideways overlap of p-orbitals.

Step 2: Analyze the types of bonding.
- - : This type of bonding occurs between two parallel p-orbitals, but it is not involved in Cl–O bonds in chlorine oxyacids.
- - : This is the correct description for the Cl–O bond, where a sigma bond and a pi bond are formed due to the hybridization and electron overlap.
- - : This would imply that the sigma bond is formed before the pi bond, which is incorrect in this case.
- None of the above: This is incorrect since the correct bonding type is - .

Step 3: Conclusion.
The correct answer is (2), - bonding, which is present in the Cl–O bond of chlorine oxyacids.

Step 1: Understanding the Concept:
.
Step 2: Detailed Explanation:
For A:
= = (approx -826.4).
For B: (approx +180.9).
Step 3: Final Answer:
Thus, , .

Concept: Oxidising power depends on ability to gain electrons, which is influenced by bond dissociation energy and hydration energy.

Step 1: Fluorine properties:
• Low bond dissociation energy (F–F bond is weak)
• High hydration energy (F is small ion)

Step 2: Effect:
• Easy to break F–F bond → easier electron gain
• Strong hydration stabilizes F Conclusion:
Thus, fluorine is strongest oxidising agent.

Concept: Ionisation energy and electron affinity govern electron removal/addition.

Step 1: Statement I.
Removing electron from fluorine requires energy → false.

Step 2: Statement II.
Fluorine releases energy when gaining electron → false.

Step 3: Conclusion.
Both statements are false.

Concept:
• contains
•Strong oxidising agents help liberate

Step 1:

Step 2:
• is a strong fluorinating agent
•Helps release Final: