Question

Assertion (A): Cuprous salts are diamagnetic.
Reason (R): In cuprous ion, 3d-orbitals are partially filled.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

Write \( \mathrm{Cu^+} \) as \( 3d^{10} \). Is a full d-subshell partially filled or completely filled?

Answer 1

The Correct Option is C

Step 1: Find the electronic configuration of the cuprous ion:
Copper has atomic number 29, with configuration \( [\mathrm{Ar}]\,3d^{10}4s^{1} \). Cuprous means \( \mathrm{Cu^+} \). It loses the 4s electron, so \( \mathrm{Cu^+} = [\mathrm{Ar}]\,3d^{10} \).

Step 2: Check the Assertion (A):
In \( 3d^{10} \) every one of the five d-orbitals holds a pair of electrons. There is no unpaired electron, so the magnetic moment is zero. Cuprous salts are therefore diamagnetic. (A) is TRUE.

Step 3: Check the Reason (R):
The reason says the 3d-orbitals are partially filled. But \( 3d^{10} \) is a completely filled set. So (R) is FALSE.

Step 4: Compare the two statements:
The assertion is true because the d-orbitals are completely filled, not partially filled. So (R) does not explain (A), it contradicts it. This matches option (C).

Final Answer:
(A) is true and (R) is false. \[ \boxed{\text{Option (C)}} \]