Question

What is the spin-only magnetic moment value (BM) of a divalent metal ion with atomic number 25, in its aqueous solution?

• A. 5.92
• B. 5.26
• C. Zero
• D. 5.0

Answer 1

The correct option is A

5.92

Explanation:

Step 1: Identifying the number of unpaired electrons

• The element of atomic number 25 is Manganese(Mn)
• Electronic configuration: $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^{2}3{\mathrm{d}}^5$
• A divalent ion means the ion formed by losing two electrons.
• So, the electronic configuration of divalent ion: $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^{6}4{\mathrm{s}}^{0}3{\mathrm{d}}^5$
• So, there are five unpaired electrons present in the valence shell.

Step 2: Calculating the spin-only magnetic moment

The formula for calculating spin-only magnetic moment is:

$$\begin{gathered} \mathrm{\mu }=\sqrt{\mathrm{n}(\mathrm{n}+2)} \\ \mathrm{\mu }=\sqrt{5(5+2)} \\ \mathrm{\mu }=\sqrt{5\times 7} \\ \mathrm{\mu }=\sqrt{35} \\ \mathrm{\mu }=5.91 \end{gathered}$$

Therefore, the correct option is A.