Which of the following has maximum number of unpaired electrons ?

Options

A. `Mg^(2+)`
B. `Ti^(3+)`
C. `Fe^(2+)`
D. `Mn^(2+)`

Answer

To determine which of the given ions has the maximum number of unpaired electrons, we will analyze the electronic configurations of each ion step by step.

### Step 1: Analyze Magnesium (Mg²⁺)
- **Atomic Number of Magnesium (Mg)**: 12
- **Electronic Configuration**: 1s² 2s² 2p⁶ 3s²
- **For Mg²⁺**: We remove 2 electrons (from the 3s orbital).
- **Electronic Configuration of Mg²⁺**: 1s² 2s² 2p⁶ (3s and 3p are empty)
- **Unpaired Electrons**: 0 (All electrons are paired)

### Step 2: Analyze Titanium (Ti³⁺)
- **Atomic Number of Titanium (Ti)**: 22
- **Electronic Configuration**: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d² 4s²
- **For Ti³⁺**: We remove 3 electrons (2 from 4s and 1 from 3d).
- **Electronic Configuration of Ti³⁺**: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹
- **Unpaired Electrons**: 1 (1 unpaired electron in 3d)

### Step 3: Analyze Iron (Fe²⁺)
- **Atomic Number of Iron (Fe)**: 26
- **Electronic Configuration**: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶
- **For Fe²⁺**: We remove 2 electrons (from 4s).
- **Electronic Configuration of Fe²⁺**: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ (4s is empty)
- **Unpaired Electrons**: 4 (According to Hund's rule, the 6 electrons in 3d will fill as 1 in each of the 5 orbitals first, resulting in 4 unpaired electrons)

### Step 4: Analyze Manganese (Mn²⁺)
- **Atomic Number of Manganese (Mn)**: 25
- **Electronic Configuration**: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁵
- **For Mn²⁺**: We remove 2 electrons (from 4s).
- **Electronic Configuration of Mn²⁺**: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ (4s is empty)
- **Unpaired Electrons**: 5 (All 5 electrons in 3d are unpaired)

### Conclusion
After analyzing all the ions:
- Mg²⁺ has 0 unpaired electrons.
- Ti³⁺ has 1 unpaired electron.
- Fe²⁺ has 4 unpaired electrons.
- Mn²⁺ has 5 unpaired electrons.

**The ion with the maximum number of unpaired electrons is Mn²⁺ with 5 unpaired electrons.**

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