Transition Metals

Step 1: Understanding the Concept:
The spin-only magnetic moment ( ) is dependent on the number of unpaired electrons ( ) present in the outermost d-orbitals of the transition metal ion.
Step 2: Key Formula or Approach:
The formula for spin-only magnetic moment is:
Step 3: Detailed Explanation:
Let's evaluate the number of unpaired electrons and the theoretical magnetic moment for each given ion.
For option (A), :
The electronic configuration of Ni is .
The ion has an outer configuration of .
According to Hund's rule, filling 8 electrons in 5 d-orbitals leaves 2 unpaired electrons ( ).
The value given in the option is 4.73, which is drastically incorrect.
For option (B), :
Configuration is , which has 4 unpaired electrons ( ).
(This is correct).
For option (C), :
Configuration is , which has 2 unpaired electrons ( ).
(This is correct).
For option (D), (Cobalt ion ):
Configuration is , which has 3 unpaired electrons ( ).
(This is approximately 3.89, so it is considered correct).
For option (E), the text says (5.92). This is a clear typographical error in the paper for (Manganese).
has a configuration with 5 unpaired electrons ( ).
Assuming the intended ion was , this value is correct.
Thus, the unequivocally incorrect value matched to the wrong ion is in option (A).
Step 4: Final Answer:
The given magnetic moment for is not correct.