Element having `(4,0,0+1//2)` as a set of four quantum numbers for its valence electron is-

Answer

To determine the element that corresponds to the set of quantum numbers (4, 0, 0, +1/2), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Principal Quantum Number (n)**:
- The first quantum number is 4, which indicates that the principal quantum number \( n = 4 \). This means the electron is in the fourth energy level.

2. **Identify the Azimuthal Quantum Number (l)**:
- The second quantum number is 0, which corresponds to the azimuthal quantum number \( l = 0 \). This indicates that the electron is in an s orbital (since \( l = 0 \) represents s orbitals).

3. **Determine the Magnetic Quantum Number (m)**:
- The third quantum number is also 0, which means the magnetic quantum number \( m_l = 0 \). This is consistent with the s orbital, which has only one orientation.

4. **Identify the Spin Quantum Number (s)**:
- The fourth quantum number is +1/2, indicating that the spin quantum number \( s = +1/2 \). This means the electron has an upward spin.

5. **Determine the Electron Configuration**:
- Since we have determined that the electron is in the 4s orbital, we need to consider how many electrons can occupy this orbital. The 4s orbital can hold a maximum of 2 electrons.
- If there is 1 electron in the 4s orbital, the configuration would be \( 4s^1 \), which corresponds to Potassium (K).
- If there are 2 electrons in the 4s orbital, the configuration would be \( 4s^2 \), which corresponds to Calcium (Ca).

6. **Conclusion**:
- Therefore, the element with the given quantum numbers could either be Potassium (K) or Calcium (Ca), depending on whether the 4s orbital has 1 or 2 electrons.

### Final Answer:
The element having the quantum numbers (4, 0, 0, +1/2) is either Potassium (K) or Calcium (Ca).