Question

Which one of the following ions has the maximum number of unpaired electrons?

• A. Cu\(^{2+}\)
• B. Na\(^{+}\)
• C. Cr\(^{3+}\)
• D. Fe\(^{3+}\)

Hint:

To find the number of unpaired electrons, write the electron configuration and count the electrons in degenerate orbitals.

Answer 1

The Correct Option is D

Step 1: Understanding electron configuration. 
To determine the number of unpaired electrons, we need to look at the electron configurations of the ions: 

- Cu\(^{2+}\) has the electron configuration [Ar] 3d\(^9\), which has one unpaired electron. 

- Na\(^{+}\) has the electron configuration [Ne], which has no unpaired electrons. 

- Cr\(^{3+}\) has the electron configuration [Ar] 3d\(^3\), which has three unpaired electrons. 

- Fe\(^{3+}\) has the electron configuration [Ar] 3d\(^5\), which has five unpaired electrons. 
 

Step 2: Conclusion. 
The correct answer is (D) Fe\(^{3+}\), which has the maximum number of unpaired electrons.