The incorrect statement among the following

Options

A. The first ionization potential of Al is less than the first ionization potential of Mg
B. The second ionization potential of Mg is greater than the second ionization potential of Na
C. The first ionization potential of Na is less than the first ionization potential of Mg
D. The third ionization potential of Mg is greater than the third ionization potential of Al

Explanation

To determine the incorrect statement among the provided options regarding ionization potentials, we will analyze each statement step-by-step.

### Step 1: Understanding Ionization Energy
- **Definition**: Ionization energy (or ionization potential) is the minimum amount of energy required to remove an outermost electron from an isolated gaseous atom.
- **First Ionization Energy**: This refers specifically to the energy needed to remove the first electron from an atom.

### Step 2: Analyzing the First Statement
- **Statement**: The first ionization potential of Aluminium (Al) is less than that of Magnesium (Mg).
- **Electronic Configurations**:
- Aluminium: 1s² 2s² 2p⁶ 3s² 3p¹
- Magnesium: 1s² 2s² 2p⁶ 3s²
- **Analysis**:
- Aluminium has three valence electrons (in the 3s and 3p orbitals), while Magnesium has two (in the 3s orbital).
- Removing an electron from Aluminium (3p¹) requires less energy than removing one from Magnesium (3s²), which is more stable.
- **Conclusion**: The statement is **correct**.

### Step 3: Analyzing the Second Statement
- **Statement**: The second ionization potential of Magnesium is greater than that of Sodium (Na).
- **Electronic Configurations**:
- Sodium: 1s² 2s² 2p⁶ 3s¹
- Magnesium: 1s² 2s² 2p⁶ 3s²
- **Analysis**:
- After losing one electron, Sodium becomes Na⁺ (1s² 2s² 2p⁶) and Magnesium becomes Mg⁺ (1s² 2s² 2p⁶ 3s¹).
- Removing a second electron from Na⁺ (which has a full outer shell) requires more energy than removing from Mg⁺ (which still has an electron in the 3s orbital).
- **Conclusion**: The statement is **incorrect**.

### Step 4: Analyzing the Third Statement
- **Statement**: The first ionization potential of Sodium is less than that of Magnesium.
- **Analysis**:
- Sodium has one electron in its outermost shell (3s¹), while Magnesium has two (3s²).
- It is easier to remove the single outer electron from Sodium than to remove one from Magnesium.
- **Conclusion**: The statement is **correct**.

### Step 5: Analyzing the Fourth Statement
- **Statement**: The third ionization potential of Magnesium is greater than that of Aluminium.
- **Analysis**:
- After losing two electrons, Magnesium becomes Mg²⁺ (1s² 2s² 2p⁶) and Aluminium becomes Al²⁺ (1s² 2s² 2p⁶ 3s¹).
- It is easier to remove an electron from Al²⁺ (which has one electron in the outer shell) than from Mg²⁺ (which has a full outer shell).
- **Conclusion**: The statement is **correct**.

### Final Conclusion
The incorrect statement among the options is the second one: "The second ionization potential of Magnesium is greater than that of Sodium."