Question

Which among the following pairs of elements in their respective oxidation states will have the same value of effective magnetic moment?

• A. Zn²⁺ and Cr³⁺
• B. Ni²⁺ and Ti³⁺
• C. Cr³⁺ and Co²⁺
• D. Sc³⁺ and Ti³⁺

Hint:

Effective magnetic moments are calculated based on the number of unpaired electrons. Ions with the same number of unpaired electrons will have the same magnetic moment.

Answer 1

The Correct Option is C

Step 1: Understanding effective magnetic moment.
The effective magnetic moment (\(\mu_{\text{eff}}\)) depends on the number of unpaired electrons. Elements with the same number of unpaired electrons will have the same effective magnetic moment. To calculate this, we use the formula: \[ \mu_{\text{eff}} = \sqrt{n(n+2)} \] where \(n\) is the number of unpaired electrons.
Step 2: Analyzing the options.
(A) Zn²⁺ and Cr³⁺: Incorrect. Zn²⁺ has no unpaired electrons (d¹⁰ configuration), while Cr³⁺ has 3 unpaired electrons. They will not have the same magnetic moment.
(B) Ni²⁺ and Ti³⁺: Incorrect. Ni²⁺ has 2 unpaired electrons, while Ti³⁺ has 1 unpaired electron. They will not have the same magnetic moment.
(C) Cr³⁺ and Co²⁺: Correct — Both Cr³⁺ (d⁵) and Co²⁺ (d⁷) have 3 unpaired electrons, which results in the same effective magnetic moment.
(D) Sc³⁺ and Ti³⁺: Incorrect. Sc³⁺ has no unpaired electrons (d⁰), while Ti³⁺ has 1 unpaired electron. They will not have the same magnetic moment.
Step 3: Conclusion.
The correct answer is (C) Cr³⁺ and Co²⁺, as both ions have the same number of unpaired electrons, leading to the same effective magnetic moment.