To solve the question of choosing the correct statement among the given options, we will analyze each statement regarding ionization energies of the elements mentioned.
### Step-by-Step Solution:
1. **Understanding Ionization Energy**:
- Ionization energy is defined as the energy required to remove the outermost electron from an atom in its gaseous state.
2. **Analyzing Statement 1**:
- **Statement**: The first ionization energy of sodium (Na) and magnesium (Mg).
- **Analysis**: Sodium (Na) is an alkali metal with the electron configuration [Ne]3s¹, while magnesium (Mg) is an alkaline earth metal with the configuration [Ne]3s². Since magnesium has a fully filled outer shell (3s²), it has a higher ionization energy compared to sodium, which has only one electron in its outer shell.
- **Conclusion**: This statement is **correct**.
3. **Analyzing Statement 2**:
- **Statement**: The third ionization energy of magnesium (Mg) and aluminum (Al).
- **Analysis**: Magnesium has the configuration [Ne]3s². After removing two electrons (first and second ionization), we are left with Mg²⁺ ([Ne]). The third ionization energy involves removing an electron from a stable noble gas configuration, which requires a significant amount of energy. Aluminum has the configuration [Ne]3s²3p¹. After removing two electrons, we get Al²⁺ ([Ne]3s²), and removing a third electron from Al³⁺ is easier than from Mg²⁺. Thus, the third ionization energy of magnesium is higher than that of aluminum.
- **Conclusion**: This statement is **correct**.
4. **Analyzing Statement 3**:
- **Statement**: The first ionization energy of magnesium (Mg) and aluminum (Al).
- **Analysis**: Magnesium has a stable configuration of [Ne]3s², while aluminum has [Ne]3s²3p¹. Removing an electron from aluminum is easier because it can achieve a stable noble gas configuration by losing its 3p electron. Therefore, magnesium has a higher first ionization energy than aluminum.
- **Conclusion**: This statement is **correct**.
5. **Analyzing Statement 4**:
- **Statement**: The second ionization energy of nitrogen (N) and oxygen (O).
- **Analysis**: Nitrogen has the configuration [He]2s²2p³, and after the first ionization, it becomes [He]2s²2p². Oxygen has the configuration [He]2s²2p⁴, and after the first ionization, it becomes [He]2s²2p³. The second ionization energy for nitrogen involves removing an electron from a half-filled p subshell (which is stable), while for oxygen, it involves removing an electron from a less stable configuration. Thus, the second ionization energy of nitrogen is higher than that of oxygen.
- **Conclusion**: This statement is **incorrect**.
### Final Conclusion:
The correct statements are:
- Statement 1: Correct
- Statement 2: Correct
- Statement 3: Correct
- Statement 4: Incorrect
Thus, the correct options are **1, 2, and 3**.
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