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 configuration of the `Fe^(3+)` ion, we will follow these steps:

### Step 1: Write the ground state electronic configuration of neutral Iron (Fe)
The atomic number of Iron (Fe) is 26, which means it has 26 electrons. The ground state electronic configuration of Fe can be written as:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶

### Step 2: Identify the charge of the ion
The ion we are dealing with is `Fe^(3+)`, which indicates that Iron has lost 3 electrons.

### Step 3: Remove electrons to account for the positive charge
When removing electrons to form a cation, we first remove the electrons from the outermost shell. In the case of Iron, the outermost shell is the 4s orbital.

1. Remove 2 electrons from the 4s²:
- 4s² → 4s⁰ (we do not need to write 4s⁰)

2. Now we need to remove 1 more electron from the next outermost shell, which is the 3d orbital:
- 3d⁶ → 3d⁵

### Step 4: Write the final electronic configuration for `Fe^(3+)`
After removing 3 electrons (2 from 4s and 1 from 3d), the electronic configuration of `Fe^(3+)` becomes:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵

### Step 5: Simplify the configuration using the nearest noble gas
The configuration can be simplified by using the nearest noble gas, which is Argon (Ar, atomic number 18):
- Therefore, we can write the configuration as:
- [Ar] 3d⁵

### Final Answer
The ground state configuration of `Fe^(3+)` ion in gaseous state is:
- **[Ar] 3d⁵**

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