The correct electronic configuration of lanthanum is

Options

A. `[Xe]5d^(1)6s^(2)`
B. `[Xe]4d^(1)5s^(2)`
C. `[Xe]4f^(1)5s^(2)`
D. `[Xe]5f^(1)6s^(2)`

Answer

To determine the correct electronic configuration of lanthanum (La), we follow these steps:

### Step 1: Identify the Atomic Number
Lanthanum has an atomic number of 57. This means it has 57 electrons.

### Step 2: Write the Electronic Configuration
We start filling the electron orbitals in order of increasing energy levels:

1. **1s orbital**: 2 electrons → 1s²
2. **2s orbital**: 2 electrons → 2s²
3. **2p orbital**: 6 electrons → 2p⁶
4. **3s orbital**: 2 electrons → 3s²
5. **3p orbital**: 6 electrons → 3p⁶
6. **4s orbital**: 2 electrons → 4s²
7. **3d orbital**: 10 electrons → 3d¹⁰
8. **4p orbital**: 6 electrons → 4p⁶
9. **4d orbital**: 10 electrons → 4d¹⁰
10. **5s orbital**: 2 electrons → 5s²

At this point, we have filled:
- 2 (1s) + 2 (2s) + 6 (2p) + 2 (3s) + 6 (3p) + 2 (4s) + 10 (3d) + 6 (4p) + 10 (4d) + 2 (5s) = 54 electrons.

### Step 3: Fill the Remaining Electrons
Now we have 3 electrons left to place (57 - 54 = 3):
- The next available orbitals are 5d and 6s.
- We place 1 electron in the 5d orbital and 2 electrons in the 6s orbital.

### Step 4: Write the Final Electronic Configuration
Thus, the complete electronic configuration for lanthanum is:
\[ \text{[Xe]} \, 5d^1 \, 6s^2 \]

### Conclusion
The correct electronic configuration of lanthanum is:
\[ \text{[Xe]} \, 5d^1 \, 6s^2 \]