Assertion `: H_(2)` molecule is more stable than `He-H ` molecule .
Reason `:` The antibonding electron in `He-H` molecule decreases the bond order thereby the stability.

Options

A. If both `(A)` and `(R )` are correct and `(R )` is the correct explanation of `(A)`
B. If both `(A)` and `(R )` are correct and `(R )` is the correct explanation of `(A)`
C. If `(A)` is correct but `(R )` is incorrect
D. If `(A)` is incorrect but `(R )` is correct

Explanation

To solve the assertion and reason question regarding the stability of the H₂ molecule compared to the He-H molecule, we can break down the solution into clear steps:

### Step 1: Understand the Assertion
The assertion states that the H₂ molecule is more stable than the He-H molecule.

### Step 2: Analyze the H₂ Molecule
- The electronic configuration of H₂ can be represented as σ(1s)².
- In this case, there are 2 bonding electrons and no antibonding electrons.
- The bond order (B.O.) can be calculated using the formula:
\[ \text{Bond Order} = \frac{(n_b - n_a)}{2} \]
where \( n_b \) is the number of bonding electrons and \( n_a \) is the number of antibonding electrons.
- For H₂:
- \( n_b = 2 \) (bonding electrons)
- \( n_a = 0 \) (antibonding electrons)
- Therefore, the bond order is:
\[ \text{B.O.} = \frac{(2 - 0)}{2} = 1 \]

### Step 3: Analyze the He-H Molecule
- The electronic configuration of the He-H molecule can be represented as σ(1s)² σ*(1s)¹.
- Here, there are 2 bonding electrons and 1 antibonding electron.
- For He-H:
- \( n_b = 2 \) (bonding electrons)
- \( n_a = 1 \) (antibonding electrons)
- Therefore, the bond order is:
\[ \text{B.O.} = \frac{(2 - 1)}{2} = \frac{1}{2} \]

### Step 4: Compare the Bond Orders
- The bond order for H₂ is 1, while for He-H it is 0.5.
- A higher bond order indicates a stronger bond and greater stability.

### Step 5: Conclusion on Assertion
Since the bond order of H₂ is greater than that of He-H, we conclude that H₂ is indeed more stable than He-H.

### Step 6: Analyze the Reason
The reason states that the presence of an antibonding electron in the He-H molecule decreases the bond order, thereby affecting stability. This is correct because:
- Antibonding electrons reduce the overall bond strength.
- A lower bond order correlates with lower stability.

### Final Conclusion
Both the assertion and the reason are correct, and the reason correctly explains the assertion.

### Answer
The correct answer is A: Both Assertion and Reason are correct.

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