To determine the maximum number of unpaired electrons in the different oxidation states of iron (Fe), we will analyze the electron configurations step by step.
### Step 1: Determine the electron configuration of Fe
Iron (Fe) has an atomic number of 26. The electron configuration of neutral Fe is:
\[ \text{Fe: } 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 4s^2 \, 3d^6 \]
### Step 2: Analyze Fe in the +2 oxidation state (Fe²⁺)
When iron loses 2 electrons to form Fe²⁺, the electrons are removed from the outermost shell first, which is the 4s orbital. Thus, the electron configuration for Fe²⁺ becomes:
\[ \text{Fe}^{2+}: 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 3d^6 \]
In the 3d subshell, we have 6 electrons. According to Hund's rule, we fill the orbitals singly before pairing. The distribution is:
- 3d: ↑ ↑ ↑ ↑ ↑ (5 unpaired) and one paired.
Thus, Fe²⁺ has **4 unpaired electrons**.
### Step 3: Analyze Fe in the +3 oxidation state (Fe³⁺)
For Fe³⁺, we remove one more electron from the 3d subshell:
\[ \text{Fe}^{3+}: 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 3d^5 \]
In the 3d subshell, we have 5 electrons, which can be distributed as:
- 3d: ↑ ↑ ↑ ↑ ↑ (5 unpaired)
Thus, Fe³⁺ has **5 unpaired electrons**.
### Step 4: Analyze Fe in the +4 oxidation state (Fe⁴⁺)
For Fe⁴⁺, we remove one more electron, leading to:
\[ \text{Fe}^{4+}: 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 3d^4 \]
In the 3d subshell, we have 4 electrons, which can be distributed as:
- 3d: ↑ ↑ ↑ ↑ (4 unpaired) and one paired.
Thus, Fe⁴⁺ has **4 unpaired electrons**.
### Step 5: Conclusion
From the analysis:
- Fe²⁺ has 4 unpaired electrons.
- Fe³⁺ has 5 unpaired electrons.
- Fe⁴⁺ has 4 unpaired electrons.
The maximum number of unpaired electrons is found in Fe³⁺, which has **5 unpaired electrons**.
### Final Answer
The maximum number of unpaired electrons is in **Fe³⁺ (5 unpaired electrons)**.
