The number of d-electrons retained in `Fe^(2+)` (At. No Fe=26) ions are:

Options

A. `3`
B. `4`
C. `5`
D. `6`

Explanation

To determine the number of d-electrons retained in the `Fe^(2+)` ion, we can follow these steps:

### Step 1: Determine 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 (Fe) can be written as:
- **Fe:** \( [Ar] \, 3d^6 \, 4s^2 \)

This means that iron has 6 electrons in the 3d subshell and 2 electrons in the 4s subshell.

### Step 3: Identify the Oxidation State
In the question, we are dealing with the `Fe^(2+)` ion. This indicates that iron has lost 2 electrons.

### Step 4: Remove Electrons to Form the `Fe^(2+)` Ion
When forming the `Fe^(2+)` ion, we remove 2 electrons. According to the Aufbau principle, electrons are removed from the outermost shell first, which in this case is the 4s subshell before the 3d subshell:
- From \( [Ar] \, 3d^6 \, 4s^2 \), removing 2 electrons from the 4s subshell gives:
- **Fe^(2+):** \( [Ar] \, 3d^6 \, 4s^0 \)

### Step 5: Count the d-Electrons in `Fe^(2+)`
After the removal of the 4s electrons, we are left with:
- **3d electrons:** 6

Thus, the number of d-electrons retained in the `Fe^(2+)` ion is **6**.

### Final Answer
The number of d-electrons retained in `Fe^(2+)` is **6**.

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