Assertion: Mercurous compounds are diamagnetic.
Reason: Two `Hg^(o+)` species which have `6s^1` configuration are bonded together using s-electrons.

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, but (R) is not the correct explanation of (A).
C. If (A) is correct, but (R) is incorrect.
D. If (A) is incorrect but (R) is correct.

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states that "Mercurous compounds are diamagnetic."

- **Definition of Diamagnetic**: A substance is diamagnetic if it has no unpaired electrons in its atomic or molecular structure. This leads to a magnetic moment of zero.

### Step 2: Analyze Mercurous Compounds
Mercurous compounds contain mercury in the +1 oxidation state, represented as Hg(I).

- **Electronic Configuration of Mercury**: The atomic number of mercury (Hg) is 80. Its electron configuration is:
- \( \text{[Xe]} \, 4f^{14} \, 5d^{10} \, 6s^{2} \)

- **In the +1 Oxidation State**: When mercury loses one electron to form Hg(I), its configuration becomes:
- \( \text{[Xe]} \, 4f^{14} \, 5d^{10} \, 6s^{1} \)

### Step 3: Determine the Magnetic Properties
In the +1 oxidation state (Hg(I)), there is one unpaired electron in the 6s orbital.

- **Conclusion for Assertion**: Since there is an unpaired electron in Hg(I), mercurous compounds should be paramagnetic, not diamagnetic. Thus, the assertion is **false**.

### Step 4: Understand the Reason
The reason states that "Two Hg(I) species which have 6s¹ configuration are bonded together using s-electrons."

- **Formation of Mercurous Ion**: In mercurous compounds, two Hg(I) ions can bond together to form the mercurous ion \( \text{Hg}_2^{2+} \). Each Hg(I) contributes its single unpaired electron to form a bond, resulting in no unpaired electrons in the mercurous ion.

### Step 5: Determine the Magnetic Properties of Mercurous Ion
In the mercurous ion \( \text{Hg}_2^{2+} \):
- The two unpaired electrons from each Hg(I) ion pair up to form a bond, leading to a situation where there are no unpaired electrons.

- **Conclusion for Reason**: This means that the mercurous ion is indeed diamagnetic, making the reason **true**.

### Final Conclusion
- The assertion is **false** (mercurous compounds are not diamagnetic).
- The reason is **true** (the bonding of two Hg(I) ions results in no unpaired electrons).

### Answer
Both statements cannot be true simultaneously, so the correct option would be that the assertion is false and the reason is true.