To determine whether the first ionization potential (I.P.) of magnesium (Mg) is greater than, less than, or equal to that of aluminum (Al), we can follow these steps:
### Step-by-Step Solution:
1. **Understand Ionization Potential**:
- Ionization potential (or ionization energy) is the energy required to remove the outermost electron from a neutral atom. A higher ionization potential means it is more difficult to remove an electron.
2. **Write Electronic Configurations**:
- For magnesium (Mg), the atomic number is 12. Its electronic configuration is:
\[
\text{Mg: } 1s^2 \, 2s^2 \, 2p^6 \, 3s^2
\]
- For aluminum (Al), the atomic number is 13. Its electronic configuration is:
\[
\text{Al: } 1s^2 \, 2s^2 \, 2p^6 \, 3s^2 \, 3p^1
\]
3. **Analyze the Outermost Electrons**:
- In magnesium, the outermost electrons are in the 3s subshell (2 electrons).
- In aluminum, the outermost electrons are in the 3s subshell (2 electrons) and one in the 3p subshell (1 electron).
4. **Stability of Electron Configurations**:
- The 3s subshell in magnesium is fully filled (2 electrons), which provides a stable configuration.
- In aluminum, the presence of an electron in the 3p subshell means it is less stable compared to magnesium's configuration.
5. **Ease of Electron Removal**:
- Since magnesium has a fully filled 3s subshell, it is more stable and requires more energy to remove an electron compared to aluminum, which has an unfilled 3p subshell.
- Therefore, it is easier to remove an electron from aluminum than from magnesium.
6. **Conclusion**:
- Since it is easier to remove an electron from aluminum, the first ionization potential of magnesium is greater than that of aluminum.
- Thus, we conclude:
\[
\text{First Ionization Potential of Mg is greater than that of Al.}
\]
### Final Answer:
The first ionization potential of magnesium (Mg) is **greater** than that of aluminum (Al).
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