`4s` orbitals has less energy than `3d` orbital

Explanation

To determine whether the statement "4s orbital has less energy than 3d orbital" is true or false, we can use the n + l rule, which helps us compare the energy levels of different orbitals.

### Step-by-Step Solution:

1. **Identify the Quantum Numbers**:
- For the **4s orbital**:
- Principal quantum number (n) = 4
- Azimuthal quantum number (l) = 0 (since it's an s orbital)
...