the ground state electronic configuration of chromium can be written as

Options

A. `[Ar] 3d^1 4s^1`
B. `[Ar] 3d^1 4s^2`
C. `[Ar] 3d^5 4s^1`
D. `[Ne] 3d^4 4s^1`

Answer

To determine the ground state electronic configuration of chromium (Cr), we need to follow these steps:

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

### Step 2: Write the Basic Electron Configuration
Using the Aufbau principle, we fill the electron orbitals in order of increasing energy levels. The order of filling is as follows:
1. 1s
2. 2s
3. 2p
4. 3s
5. 3p
6. 4s
7. 3d

Following this order, the basic electron configuration without considering any exceptions would be:
- 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁴

### Step 3: Adjust for Stability
However, chromium is an exception to the expected electron configuration due to stability preferences. It is more stable to have a half-filled d subshell. Therefore, instead of having 3d⁴, chromium will have 3d⁵.

### Step 4: Write the Final Configuration
Thus, the correct ground state electronic configuration for chromium is:
- [Ar] 3d⁵ 4s¹

Where [Ar] represents the electron configuration of argon, which accounts for the first 18 electrons.

### Final Answer
The ground state electronic configuration of chromium can be written as:
- [Ar] 3d⁵ 4s¹

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