Which of the following statements is incorrect?

Options

A. The second ionization energy of sulphur is greater than that of chlorine
B. The third ionization energy of phosphorus is greater than that of aluminium
C. The first ionization energy of aluminium is approximately the same as that of gallium
D. The second ionization energy of boron is greater than that of carbon

Answer

To determine which of the statements is incorrect, we will analyze each statement regarding ionization energies and electronic configurations.

### Step 1: Analyze the first statement
**Statement:** The second ionization energy of sulfur is greater than that of chlorine.

- **Electronic Configuration:**
- Sulfur (S, atomic number 16): 1s² 2s² 2p⁶ 3s² 3p⁴
- Chlorine (Cl, atomic number 17): 1s² 2s² 2p⁶ 3s² 3p⁵

- **Analysis:**
- The second ionization energy refers to removing the second electron after the first has already been removed.
- For sulfur, after removing one electron, it has a half-filled p subshell (3p³), which is relatively stable.
- For chlorine, after removing one electron, it has a configuration of 3p⁴, which is less stable than sulfur's configuration.

- **Conclusion:** The statement is correct; the second ionization energy of sulfur is indeed greater than that of chlorine.

### Step 2: Analyze the second statement
**Statement:** The third ionization energy of phosphorus is greater than that of aluminum.

- **Electronic Configuration:**
- Phosphorus (P, atomic number 15): 1s² 2s² 2p⁶ 3s² 3p³
- Aluminum (Al, atomic number 13): 1s² 2s² 2p⁶ 3s² 3p¹

- **Analysis:**
- The third ionization energy involves removing a third electron.
- For phosphorus, removing the third electron means disrupting a half-filled p subshell (3p³), which requires more energy.
- For aluminum, the third ionization involves removing an electron from a filled 3s subshell, which is less stable than the half-filled state of phosphorus.

- **Conclusion:** This statement is incorrect; the third ionization energy of phosphorus is actually greater than that of aluminum.

### Step 3: Analyze the third statement
**Statement:** The first ionization energy of aluminum is approximately the same as gallium.

- **Electronic Configuration:**
- Gallium (Ga, atomic number 31): 1s² 2s² 2p⁶ 3s² 3p¹

- **Analysis:**
- Both aluminum and gallium are in the same group (Group 13) and have similar outer electron configurations.
- The first ionization energy will be similar due to their comparable sizes and electronic configurations.

- **Conclusion:** This statement is correct; the first ionization energy of aluminum is approximately the same as that of gallium.

### Step 4: Analyze the fourth statement
**Statement:** The second ionization energy of boron is greater than that of carbon.

- **Electronic Configuration:**
- Boron (B, atomic number 5): 1s² 2s² 2p¹
- Carbon (C, atomic number 6): 1s² 2s² 2p²

- **Analysis:**
- The second ionization energy refers to removing a second electron.
- For boron, after removing one electron, it has a filled 2s subshell and a half-filled 2p subshell.
- For carbon, removing the second electron involves disrupting a filled 2s subshell, which is more stable than boron’s configuration.

- **Conclusion:** This statement is correct; the second ionization energy of boron is indeed greater than that of carbon.

### Final Conclusion
After analyzing all statements, the incorrect statement is:

**The third ionization energy of phosphorus is greater than that of aluminum.**