Amongst the following, the incorrect statement is

Options

A. `IE_(1) (Al)lt IE_(1) (Mg)`
B. `IE_(1) (Na)lt IE_(1) (Mg)`
C. `IE_(2) (Mg)lt IE_(2) (Na)`
D. `IE_(3)(Mg)gtIE_(3)(Al)`

Answer

To solve the question about which statement is incorrect among the given options regarding ionization energies of aluminum, sodium, and magnesium, we can analyze each statement step by step.

### Step 1: Analyze the First Statement
**Statement:** The first ionization energy of aluminum is less than that of magnesium.

- **Explanation:** Aluminum (Al) has an electronic configuration of [Ne]3s²3p¹, while magnesium (Mg) has [Ne]3s². Magnesium has a completely filled 3s subshell, which is more stable than the partially filled 3p subshell of aluminum. Therefore, it requires more energy to remove an electron from magnesium than from aluminum.
- **Conclusion:** This statement is **correct**.

### Step 2: Analyze the Second Statement
**Statement:** The first ionization energy of sodium is less than that of magnesium.

- **Explanation:** Sodium (Na) has an electronic configuration of [Ne]3s¹. Magnesium, as mentioned, has a more stable configuration with [Ne]3s². Since sodium has one less electron and is located further left in the periodic table, it has a lower ionization energy compared to magnesium.
- **Conclusion:** This statement is **correct**.

### Step 3: Analyze the Third Statement
**Statement:** The second ionization energy of magnesium is greater than that of sodium.

- **Explanation:** After the first ionization, magnesium becomes [Ne]3s¹ (removing one electron from 3s²), while sodium becomes [Ne]3s⁰ (removing one electron from 3s¹). To remove another electron from magnesium (which is still partially filled), it requires less energy compared to removing an electron from sodium, which now has a stable noble gas configuration ([Ne]2p⁶). Thus, sodium's second ionization energy is higher.
- **Conclusion:** This statement is **incorrect**.

### Step 4: Analyze the Fourth Statement
**Statement:** The third ionization energy of magnesium is greater than that of aluminum.

- **Explanation:** After losing two electrons, magnesium becomes [Ne]3s⁰, while aluminum becomes [Ne]3s¹. Removing an electron from a filled subshell (magnesium) generally requires more energy than removing from a partially filled subshell (aluminum). Therefore, magnesium's third ionization energy is indeed higher.
- **Conclusion:** This statement is **correct**.

### Final Conclusion
The incorrect statement among the options provided is the third one: "The second ionization energy of magnesium is greater than that of sodium."