Which of the following has maximum number of unpaired electron (atomic number of `Fe 26`)

Options

A. `Fe`
B. `Fe(II)`
C. `Fe(III)`
D. `Fe(IV)`

Explanation

To determine which of the given options has the maximum number of unpaired electrons, we first need to analyze the electronic configuration of the element with atomic number 26, which is Iron (Fe).

### Step 1: Write the Electronic Configuration of Fe
The electronic configuration of Iron (Fe) with atomic number 26 is:
\[ \text{Fe: } 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 4s^2 \, 3d^6 \]

### Step 2: Identify Unpaired Electrons in Fe
In the 3d subshell, there are 6 electrons. According to Hund's rule, we fill each orbital singly before pairing them. The distribution of the 6 electrons in the 3d subshell is as follows:
- 3d has 5 orbitals, and we can fill them with 1 electron each before pairing.
- So, the filling will be: ↑ ↑ ↑ ↑ ↑ (5 electrons in separate orbitals) and then we pair the last electron: ↑↑.

Thus, in the 3d subshell, there are 4 unpaired electrons.

### Step 3: Analyze Each Given Option
1. **Fe**: 4 unpaired electrons (as calculated above).
2. **Fe + 2**: Removing 2 electrons from the 4s subshell (which is emptied) leaves us with the configuration:
\[ 3d^6 \]
- Unpaired electrons = 4 (same as Fe).

3. **Fe + 3**: Removing 2 electrons from the 4s and 1 from the 3d subshell gives us:
\[ 3d^5 \]
- Unpaired electrons = 5 (since all 5 electrons in 3d are unpaired).

4. **Fe + 4**: Removing 2 electrons from the 4s and 2 from the 3d gives us:
\[ 3d^4 \]
- Unpaired electrons = 4 (since 4 electrons can be placed in separate orbitals).

### Step 4: Conclusion
Among the options analyzed:
- Fe has 4 unpaired electrons.
- Fe + 2 has 4 unpaired electrons.
- Fe + 3 has 5 unpaired electrons.
- Fe + 4 has 4 unpaired electrons.

Thus, the option with the maximum number of unpaired electrons is **Fe + 3**, which has **5 unpaired electrons**.

### Final Answer
The option with the maximum number of unpaired electrons is **Fe + 3**.

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