The outer electronic configuration of chromium is

Options

A. `4s^2 3d^5`
B. `4s^1 3d^5`
C. `4s^2 3d^4`
D. `4s^2 3d^6`

Answer

To determine the outer electronic configuration of chromium, we will follow these steps:

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

### Step 2: Write the Electronic Configuration
The electronic configuration of chromium can be derived by filling the orbitals according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle. The general order of filling is:
1s, 2s, 2p, 3s, 3p, 4s, 3d.

Filling the electrons:
- 1s² (2 electrons)
- 2s² (2 electrons)
- 2p⁶ (6 electrons)
- 3s² (2 electrons)
- 3p⁶ (6 electrons)
- 4s² (2 electrons)
- 3d⁴ (4 electrons)

This gives us a preliminary configuration of:
\[ \text{Ar} \, 3d^4 \, 4s^2 \]

### Step 3: Adjust for Stability
However, chromium is known to have a unique configuration due to stability reasons. Instead of the expected \(3d^4 \, 4s^2\), chromium actually has the configuration \(3d^5 \, 4s^1\). This is because half-filled (3d⁵) and fully filled (4s²) orbitals provide extra stability.

### Step 4: Identify the Outer Electronic Configuration
The outer electronic configuration refers to the highest energy level orbitals, which are \(4s\) and \(3d\). Therefore, the outer electronic configuration of chromium is:
\[ 4s^1 \, 3d^5 \]

### Final Answer
The outer electronic configuration of chromium is:
\[ 4s^1 \, 3d^5 \]

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