The highest number of unpaired electrons are present in

Options

A. `Fe^(0)`
B. `Fe^(4+)`
C. `Fe^(2+)`
D. `Fe^(3+)`

Explanation

To determine which species has the highest number of unpaired electrons, we will analyze the electron configurations of the given oxidation states of iron (Fe).

### Step-by-Step Solution:

1. **Identify the Electron Configuration of Neutral Iron (Fe):**
- Iron has an atomic number of 26. Therefore, its electron configuration is:
\[ \text{Fe: } 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6 \]
- In the outermost shell, we have 4s² and 3d⁶.

2. **Apply Hund's Rule to Determine Unpaired Electrons in Neutral Iron:**
- According to Hund's rule, we fill each orbital singly before pairing. The 3d subshell has 5 orbitals.
- Filling the 3d electrons:
- 1 electron in each of the 5 orbitals gives us 5 unpaired electrons.
- Then we pair 1 of the electrons in one of the orbitals.
- Therefore, the number of unpaired electrons in neutral Fe is:
\[ \text{Unpaired Electrons in Fe} = 4 \]

3. **Calculate Unpaired Electrons in Fe²⁺:**
- For Fe²⁺, we remove 2 electrons. The configuration becomes:
\[ \text{Fe}^{2+}: 3d^6 \]
- Following the same filling method:
- 1 electron in each of the 5 orbitals gives us 5 unpaired electrons.
- Then we pair 2 of the electrons.
- Thus, the number of unpaired electrons in Fe²⁺ is:
\[ \text{Unpaired Electrons in Fe}^{2+} = 4 \]

4. **Calculate Unpaired Electrons in Fe³⁺:**
- For Fe³⁺, we remove 3 electrons. The configuration becomes:
\[ \text{Fe}^{3+}: 3d^5 \]
- Again, filling according to Hund's rule:
- Each of the 5 orbitals gets 1 electron.
- Therefore, the number of unpaired electrons in Fe³⁺ is:
\[ \text{Unpaired Electrons in Fe}^{3+} = 5 \]

5. **Compare the Number of Unpaired Electrons:**
- Neutral Fe: 4 unpaired electrons
- Fe²⁺: 4 unpaired electrons
- Fe³⁺: 5 unpaired electrons

6. **Conclusion:**
- The species with the highest number of unpaired electrons is **Fe³⁺**, which has **5 unpaired electrons**.

### Final Answer:
The highest number of unpaired electrons is present in **Fe³⁺** (5 unpaired electrons).