The ground state configuration of `Fe^(3+)` ion in gaseous state is: (At. No. of Fe = 26)

Options

A. `[Ar]^(18) 3d^(3) 4s^(2)`
B. `[Ar]^(18) 3d^(6) 4s^(2)`
C. `[Ar]^(18) 3d^(5)`
D. `[Ar]^(18) 3d^(6)`

Explanation

To determine the ground state electron configuration of the `Fe^(3+)` ion in the gaseous state, we can follow these steps:

### Step 1: Write the electron configuration of neutral iron (Fe).
- The atomic number of iron (Fe) is 26, which means it has 26 electrons.
- The electron configuration for neutral iron is:
\[ 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 4s^2 \, 3d^6 \]

### Step 2: Determine the number of electrons to remove for the `Fe^(3+)` ion.
- The `Fe^(3+)` ion indicates that iron has lost 3 electrons.

### Step 3: Remove electrons from the electron configuration.
- Electrons are removed first from the outermost shell (4s) before the d-subshell.
- Therefore, we remove 2 electrons from the 4s subshell and 1 electron from the 3d subshell:
- Remove 2 electrons from \(4s^2\) → \(4s^0\)
- Remove 1 electron from \(3d^6\) → \(3d^5\)

### Step 4: Write the new electron configuration for `Fe^(3+)`.
- After removing the electrons, the configuration becomes:
\[ 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^6 \, 3d^5 \]

### Step 5: Simplify the configuration using noble gas notation.
- The electron configuration can be represented using the noble gas argon (Ar), which has an atomic number of 18:
\[ [Ar] \, 3d^5 \]

### Final Answer:
The ground state configuration of the `Fe^(3+)` ion in the gaseous state is:
\[ [Ar] \, 3d^5 \]

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