First I.P. of Mg is ............. than that of Al

Options

A. Less
B. More
C. Equal
D. None of these

Answer

To determine whether the first ionization potential (I.P.) of magnesium (Mg) is greater than or less than that of aluminum (Al), we can follow these steps:

### Step-by-Step Solution:

1. **Define Ionization Potential**:
- Ionization potential is the amount of energy required to remove an electron from an atom in its gaseous state.

2. **Identify Atomic Numbers**:
- Magnesium (Mg) has an atomic number of 12.
- Aluminum (Al) has an atomic number of 13.

3. **Write Electron Configurations**:
- For Magnesium (Mg):
- The electron configuration is 1s² 2s² 2p⁶ 3s².
- For Aluminum (Al):
- The electron configuration is 1s² 2s² 2p⁶ 3s² 3p¹.

4. **Analyze the Valence Electrons**:
- Magnesium has 2 electrons in the 3s subshell (3s²), which is a completely filled subshell.
- Aluminum has 3 electrons in the 3s and 3p subshells (3s² 3p¹), with one unpaired electron in the 3p subshell.

5. **Consider Stability of Electron Configurations**:
- A completely filled subshell (like in Mg) is more stable compared to a partially filled subshell (like in Al).
- Removing an electron from a stable configuration (Mg) requires more energy than removing an electron from a less stable configuration (Al).

6. **Compare Ionization Potentials**:
- Since magnesium has a stable electron configuration with a filled 3s subshell, it will have a higher ionization potential compared to aluminum, which has an unpaired electron in the 3p subshell.

7. **Conclusion**:
- Therefore, the first ionization potential of magnesium (Mg) is **greater than** that of aluminum (Al).

### Final Answer:
The first I.P. of Mg is **greater** than that of Al.

---