Which of the following has the maximum number of unpaired d-electron?

Options

A. `Zn^(2+)`
B. `Fe^(2+)`
C. `Ni^(3+)`
D. `Cu^(+)`

Explanation

To solve the problem of determining which ion has the maximum number of unpaired d-electrons, we will analyze the electronic configurations of the given ions step by step.

### Step 1: Identify the Ions and Their Atomic Numbers
We need to consider the following ions:
1. Zn²⁺
2. Fe²⁺
3. Ni³⁺
4. Cu⁺

The atomic numbers of these elements are:
- Zinc (Zn): 30
- Iron (Fe): 26
- Nickel (Ni): 28
- Copper (Cu): 29

### Step 2: Write the Electronic Configurations
We will write the electronic configurations for each ion after accounting for the loss of electrons.

1. **Zn²⁺ (Zinc)**
- Atomic number: 30
- Electronic configuration of Zn: [Ar] 3d¹⁰ 4s²
- After losing 2 electrons (from 4s):
- Zn²⁺: [Ar] 3d¹⁰
- **Unpaired d-electrons: 0**

2. **Fe²⁺ (Iron)**
- Atomic number: 26
- Electronic configuration of Fe: [Ar] 3d⁶ 4s²
- After losing 2 electrons (from 4s):
- Fe²⁺: [Ar] 3d⁶
- Filling the d-orbitals:
- 3d: ↑↓ ↑↓ ↑ ↑ ↑ (4 unpaired electrons)
- **Unpaired d-electrons: 4**

3. **Ni³⁺ (Nickel)**
- Atomic number: 28
- Electronic configuration of Ni: [Ar] 3d⁸ 4s²
- After losing 3 electrons (2 from 4s and 1 from 3d):
- Ni³⁺: [Ar] 3d⁷
- Filling the d-orbitals:
- 3d: ↑↓ ↑↓ ↑ ↑ ↑ (3 unpaired electrons)
- **Unpaired d-electrons: 3**

4. **Cu⁺ (Copper)**
- Atomic number: 29
- Electronic configuration of Cu: [Ar] 3d¹⁰ 4s¹
- After losing 1 electron (from 4s):
- Cu⁺: [Ar] 3d¹⁰
- **Unpaired d-electrons: 0**

### Step 3: Compare the Number of Unpaired d-Electrons
Now we summarize the number of unpaired d-electrons for each ion:
- Zn²⁺: 0 unpaired electrons
- Fe²⁺: 4 unpaired electrons
- Ni³⁺: 3 unpaired electrons
- Cu⁺: 0 unpaired electrons

### Conclusion
The ion with the maximum number of unpaired d-electrons is **Fe²⁺**, which has **4 unpaired d-electrons**.

### Answer
**Fe²⁺ has the maximum number of unpaired d-electrons (4).**

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