The number of `d` electrons in `Fe^(2+)` (atomic number of `Fe = 26`) is not equal to that of the.

Options

A. p-electrons in `._(10)Ne`
B. s-electrons in `._(12)Mg`
C. d-electrons in Fe
D. p-electrons in `Cl^(-)`

Explanation

To determine the number of `d` electrons in `Fe^(2+)` and compare it with the number of `d` electrons in other species, we can follow these steps:

### Step 1: Determine the electron configuration of neutral Iron (Fe)
- The atomic number of Iron (Fe) is 26. Therefore, it has 26 electrons.
- The electron configuration of neutral Iron is:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²

### Step 2: Determine the electron configuration of `Fe^(2+)`
- When Iron loses 2 electrons to form `Fe^(2+)`, the electrons are removed from the outermost shell first, which is the 4s orbital.
- Therefore, the electron configuration of `Fe^(2+)` becomes:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶
- This means that `Fe^(2+)` has 6 electrons in the `d` orbital.

### Step 3: Identify the number of `d` electrons in other species
- We need to compare the number of `d` electrons in `Fe^(2+)` with other species. Let's consider the following:
1. **Neon (Ne)**: Atomic number 10
- Configuration: 1s² 2s² 2p⁶
- `d` electrons = 0
2. **Magnesium (Mg)**: Atomic number 12
- Configuration: 1s² 2s² 2p⁶ 3s²
- `d` electrons = 0
3. **Chloride ion (Cl⁻)**: Atomic number 17
- Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶
- `d` electrons = 0
4. **Iron (Fe)**: Neutral state
- Configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s²
- `d` electrons = 6

### Step 4: Conclusion
- The number of `d` electrons in `Fe^(2+)` is 6.
- The number of `d` electrons in Neon, Magnesium, and Chloride ion is 0.
- Therefore, the number of `d` electrons in `Fe^(2+)` is not equal to that of Neon, Magnesium, or Chloride ion.

### Final Answer
The number of `d` electrons in `Fe^(2+)` (6) is not equal to that of Neon, Magnesium, or Chloride ion (0).

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