The correct 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]3d^(5)4s^(1)`

Answer

To determine the correct electronic configuration of a chromium atom, we need to follow these steps:

### Step 1: Identify the Atomic Number
Chromium has an atomic number of 24, which means it has 24 electrons.

### Step 2: Write the Basic Electron Configuration
The basic electron configuration follows the order of filling the orbitals based on the Aufbau principle:
- 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.

So far, we have filled:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

### Step 3: Fill the 3d Orbital
After filling the above orbitals, we have used 18 electrons (2 + 2 + 6 + 2 + 6). We have 6 electrons left to place in the 3d and 4s orbitals.

Following the order, we fill the 3d orbital:
- 3d can hold 10 electrons, but we will only fill it with 6 electrons for chromium.

So, we would initially write:
- 3d⁴ (after placing 4 electrons in the 3d orbital)

### Step 4: Adjust for Stability
However, it is important to note that the 4s and 3d orbitals have very close energy levels. To achieve a more stable electron configuration, one electron from the 4s orbital is shifted to the 3d orbital.

This gives us:
- 3d⁵ (now half-filled, which is more stable)
- 4s¹ (one electron has been removed)

### Final Configuration
Thus, the final electronic configuration of chromium is:
- **1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹**

In shorthand notation, this is represented as:
- **[Ar] 3d⁵ 4s¹**

### Conclusion
The correct electronic configuration of a chromium atom is option D: **[Ar] 3d⁵ 4s¹**.

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