A: Zn (II) salts are diamagnetic
R : `Zn^(2+)` ion has one unpaired electron.

Options

A. IF both assertion & reason are true and the reason is the correct explanation of the assertion then mark
B. IF both assertion & reason are true but the reason is not the correct explanation of the assertion , then mark
C. IF assertion is true statement but reason is false , then mark
D. If both assertion and reason are false statements then mark

Answer

To solve the question regarding the assertion and reason about Zn(II) salts and the Zn²⁺ ion, we can break it down step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Zn(II) salts are diamagnetic."
- Diamagnetic substances are those that do not have any unpaired electrons in their atomic or molecular structure.

2. **Determining the Electronic Configuration of Zinc**:
- The atomic number of Zinc (Zn) is 30.
- The electronic configuration of Zn is:
\[ \text{Zn: } [\text{Ar}] 3d^{10} 4s^2 \]

3. **Finding the Electronic Configuration of Zn²⁺**:
- When Zinc loses two electrons to form Zn²⁺, these electrons are removed from the outermost shell (4s orbital) first.
- Thus, the electronic configuration for Zn²⁺ becomes:
\[ \text{Zn}^{2+}: [\text{Ar}] 3d^{10} 4s^0 \]

4. **Counting Unpaired Electrons**:
- In the Zn²⁺ ion, the 3d subshell has 10 electrons, which means all the 3d orbitals are fully filled (2 electrons in each of the 5 d orbitals).
- Therefore, there are **0 unpaired electrons** in Zn²⁺.

5. **Conclusion about Diamagnetism**:
- Since Zn²⁺ has 0 unpaired electrons, it is indeed diamagnetic.
- Thus, the assertion that "Zn(II) salts are diamagnetic" is **true**.

6. **Evaluating the Reason**:
- The reason states that "Zn²⁺ ion has one unpaired electron."
- Since we found that Zn²⁺ has 0 unpaired electrons, this statement is **false**.

7. **Final Evaluation**:
- The assertion is true, but the reason is false.
- Therefore, the correct option is: **Option 3** (Assertion is true, but reason is false).