The number of unpaired electrons in ferrous ion is

Options

A. 5
B. 2
C. 4
D. 3

Explanation

To determine the number of unpaired electrons in the ferrous ion (Fe²⁺), we can follow these steps:

### Step 1: Identify the Atomic Number of Iron
Iron (Fe) has an atomic number of 26.

### Step 2: Write the Electronic Configuration of Neutral Iron
The electronic configuration of neutral iron can be derived as follows:
- The noble gas preceding iron is Argon (Ar), which has an atomic number of 18.
- The remaining electrons fill the orbitals:
- 4s² (2 electrons)
- 3d⁶ (6 electrons)

Thus, the electronic configuration of neutral iron is:
\[ \text{Fe: } [\text{Ar}] 4s^2 3d^6 \]

### Step 3: Determine the Electronic Configuration of Ferrous Ion (Fe²⁺)
When iron loses two electrons to form the ferrous ion (Fe²⁺), the electrons are removed from the outermost shell first (4s before 3d). Therefore, the electronic configuration of Fe²⁺ is:
\[ \text{Fe}^{2+}: [\text{Ar}] 3d^6 4s^0 \]

### Step 4: Analyze the 3d Orbital for Unpaired Electrons
In the 3d subshell, there are 6 electrons. To determine how many of these are unpaired, we can visualize the distribution of electrons in the 3d orbitals:
- The 3d subshell can hold a maximum of 10 electrons and consists of 5 orbitals.
- According to Hund's rule, electrons will fill each orbital singly before pairing up.

The filling of the 3d orbitals with 6 electrons would look like this:
- Orbital 1: ↑
- Orbital 2: ↑
- Orbital 3: ↑
- Orbital 4: ↑
- Orbital 5: ↑↓

This distribution shows that there are 4 unpaired electrons (one in each of the first four orbitals and two in the fifth).

### Conclusion
The number of unpaired electrons in the ferrous ion (Fe²⁺) is **4**.

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