The correct ground state electronic configuration of chromium atom is :

Options

A. `[Ar]3d^(5)4s^(1)`
B. `[Ar]3d^(4)4s^(2)`
C. `[Ar]3d^(6)4s^(0)`
D. `[Ar]4d^(5)4s^(1)`

Explanation

To determine the correct ground state electronic configuration of a chromium atom, we can follow these steps:

### Step 1: Identify the Atomic Number
The atomic number of chromium (Cr) is 24. This means that a neutral chromium atom has 24 electrons.

### Step 2: Fill the Orbitals According to the Aufbau Principle
According to the Aufbau principle, electrons fill orbitals starting from the lowest energy level to the highest. The order of filling is as follows:
- 1s
- 2s
- 2p
- 3s
- 3p
- 4s
- 3d

### Step 3: Write the Initial Configuration
Following the order of filling:
- 1s can hold 2 electrons: 1s²
- 2s can hold 2 electrons: 2s²
- 2p can hold 6 electrons: 2p⁶
- 3s can hold 2 electrons: 3s²
- 3p can hold 6 electrons: 3p⁶
- 4s can hold 2 electrons: 4s²
- 3d can hold 10 electrons, but we will fill it according to the number of electrons we have left.

After filling the above orbitals, we have:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁴ (This accounts for 24 electrons: 2 + 2 + 6 + 2 + 6 + 2 + 4 = 24)

### Step 4: Adjust for Stability
However, it is known that half-filled and fully filled orbitals are more stable. The 3d subshell can hold a maximum of 10 electrons, and having it half-filled (5 electrons) is more stable than having it partially filled (4 electrons).

To achieve this stability, one electron from the 4s orbital can be promoted to the 3d orbital:
- Move one electron from 4s² to 3d⁴ to make it 3d⁵ and 4s¹.

### Step 5: Write the Final Configuration
Thus, the actual ground state electronic configuration of chromium is:
1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹

This can also be represented in shorthand notation using the nearest noble gas (argon):
[Ar] 3d⁵ 4s¹

### Final Answer
The correct ground state electronic configuration of a chromium atom is:
**[Ar] 3d⁵ 4s¹**

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