Electronic configuration of Cr (Z = 24) is

Options

A. `3d^(4) 4s^2`
B. `3d^(6) 4s^0`
C. `3d^(5) 4s^1`
D. none of these

Explanation

To determine the electronic configuration of Chromium (Cr), which has an atomic number of 24, we will follow these steps:

### Step-by-Step Solution:

1. **Identify the Atomic Number**:
- The atomic number of Chromium (Cr) is 24. This means it has 24 electrons.

2. **Write the Base Configuration**:
- The base electronic configuration starts with the nearest noble gas, which is Argon (Ar). Argon has an atomic number of 18, so we start with that.
- Configuration so far: \( \text{Ar} \) or \( [\text{Ne}] 3s^2 3p^6 \) = \( 1s^2 2s^2 2p^6 3s^2 3p^6 \).

3. **Add Electrons Beyond Argon**:
- After Argon, we need to fill the 3d and 4s orbitals. The order of filling is 4s before 3d according to the Aufbau principle.
- We would initially write: \( 4s^2 3d^4 \) after Argon.

4. **Consider Stability of Electron Configuration**:
- However, Chromium is an exception to the expected filling order. To achieve a more stable configuration, one electron from the 4s orbital is moved to the 3d orbital.
- This gives us a half-filled d-subshell, which is more stable.

5. **Final Configuration**:
- The final electronic configuration of Chromium is:
\[ [\text{Ar}] 3d^5 4s^1 \]

### Conclusion:
Thus, the electronic configuration of Chromium (Cr, Z = 24) is \( [\text{Ar}] 3d^5 4s^1 \).

---