Which among the following ions contain maximum number of unpaired electrons ? (At. No. Cr = 24, Ni=28, Sc=21 , Z=30)

Options

A. `Cr^(+3)`
B. `Ni^(+2)`
C. `Sc^(+2)`
D. `Zn^(+2)`

Explanation

To find which ion contains the maximum number of unpaired electrons among the given options (Cr³⁺, Ni²⁺, Sc²⁺, and Zn²⁺), we will determine the electronic configurations of each ion and count the unpaired electrons.

### Step 1: Determine the electronic configuration of Cr³⁺
- **Atomic Number of Chromium (Cr)**: 24
- **Electronic Configuration of Cr**: [Ar] 3d⁵ 4s¹ (due to the stability of half-filled d-orbitals)
- **For Cr³⁺**: We remove 3 electrons (1 from 4s and 2 from 3d).
- **Electronic Configuration of Cr³⁺**: [Ar] 3d³
- **Unpaired Electrons in Cr³⁺**: 3 unpaired electrons.

### Step 2: Determine the electronic configuration of Ni²⁺
- **Atomic Number of Nickel (Ni)**: 28
- **Electronic Configuration of Ni**: [Ar] 3d⁸ 4s²
- **For Ni²⁺**: We remove 2 electrons (both from 4s).
- **Electronic Configuration of Ni²⁺**: [Ar] 3d⁸
- **Unpaired Electrons in Ni²⁺**: 2 unpaired electrons.

### Step 3: Determine the electronic configuration of Sc²⁺
- **Atomic Number of Scandium (Sc)**: 21
- **Electronic Configuration of Sc**: [Ar] 3d¹ 4s²
- **For Sc²⁺**: We remove 2 electrons (both from 4s).
- **Electronic Configuration of Sc²⁺**: [Ar] 3d¹
- **Unpaired Electrons in Sc²⁺**: 1 unpaired electron.

### Step 4: Determine the electronic configuration of Zn²⁺
- **Atomic Number of Zinc (Zn)**: 30
- **Electronic Configuration of Zn**: [Ar] 3d¹⁰ 4s²
- **For Zn²⁺**: We remove 2 electrons (both from 4s).
- **Electronic Configuration of Zn²⁺**: [Ar] 3d¹⁰
- **Unpaired Electrons in Zn²⁺**: 0 unpaired electrons.

### Step 5: Compare the number of unpaired electrons
- **Cr³⁺**: 3 unpaired electrons
- **Ni²⁺**: 2 unpaired electrons
- **Sc²⁺**: 1 unpaired electron
- **Zn²⁺**: 0 unpaired electrons

### Conclusion
The ion with the maximum number of unpaired electrons is **Cr³⁺** with **3 unpaired electrons**.

### Final Answer
**Cr³⁺ contains the maximum number of unpaired electrons.**

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