Assertion: The spin only magnetic moment of `Sc^(3+)` is 1.73 BM.
Reason: The spin only magnetic momentum in (BM) is equal to `sqrt(n(n+2))`.

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 the spin-only magnetic moment of Sc^(3+) is 1.73 BM (Bohr Magnetons).

**Hint:** Recall that the magnetic moment is related to the number of unpaired electrons in an atom or ion.

### Step 2: Determine the Electronic Configuration of Scandium
Scandium (Sc) has the atomic number 21. Its electronic configuration is:
\[ \text{Sc: } [\text{Ar}] 4s^2 3d^1 \]

**Hint:** Remember that the electronic configuration helps us determine how many electrons are present in each subshell.

### Step 3: Determine the Configuration of Sc^(3+)
When Sc loses three electrons to form Sc^(3+), it loses the two 4s electrons and the one 3d electron. Thus, the electronic configuration of Sc^(3+) becomes:
\[ \text{Sc}^{3+}: [\text{Ar}] \]

**Hint:** Identify which electrons are lost when forming cations.

### Step 4: Identify Unpaired Electrons in Sc^(3+)
Since Sc^(3+) has the electronic configuration of argon, it has no unpaired electrons.

**Hint:** Unpaired electrons are crucial for determining magnetic properties.

### Step 5: Calculate the Spin-Only Magnetic Moment
The formula for the spin-only magnetic moment is:
\[ \mu = \sqrt{n(n + 2)} \]
where \( n \) is the number of unpaired electrons. Since \( n = 0 \) for Sc^(3+):
\[ \mu = \sqrt{0(0 + 2)} = \sqrt{0} = 0 \, \text{BM} \]

**Hint:** Substitute the value of \( n \) into the formula to find the magnetic moment.

### Step 6: Conclusion on the Assertion
Since the calculated spin-only magnetic moment is 0 BM and not 1.73 BM as stated in the assertion, the assertion is false.

### Step 7: Analyze the Reason
The reason states that the spin-only magnetic moment in BM is equal to \( \sqrt{n(n + 2)} \). This statement is correct.

**Hint:** Verify if the formula for calculating magnetic moment is accurate.

### Final Conclusion
- **Assertion:** False (the spin-only magnetic moment of Sc^(3+) is 0 BM, not 1.73 BM)
- **Reason:** True (the formula for calculating the magnetic moment is correct)

Thus, the correct answer is that the assertion is wrong and the reason is correct.

### Summary of Steps:
1. Analyze the assertion about Sc^(3+).
2. Determine the electronic configuration of Sc.
3. Find the configuration of Sc^(3+).
4. Identify the number of unpaired electrons.
5. Calculate the spin-only magnetic moment.
6. Conclude the truth of the assertion.
7. Verify the reason.