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 aluminium is greater than that of phosphorus
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

Explanation

To determine which statement is incorrect among the given options, we will analyze each statement step by step.

### Step 1: Analyze Statement A
**Statement A:** Comparison of Sulfur and Chlorine regarding their ionization energies.

- **Sulfur (S):** Electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁴.
- **Chlorine (Cl):** Electronic configuration is 1s² 2s² 2p⁶ 3s² 3p⁵.

When we consider the removal of one electron (ionization), we find:
- **S → S⁺:** 1s² 2s² 2p⁶ 3s² 3p³ (removal of one electron from 3p orbital)
- **Cl → Cl⁺:** 1s² 2s² 2p⁶ 3s² 3p⁴ (removal of one electron from 3p orbital)

Since removing an electron from a half-filled or fully filled subshell is more stable, chlorine has a higher ionization energy than sulfur. Thus, this statement is correct.

### Step 2: Analyze Statement B
**Statement B:** Comparison of Aluminum and Phosphorus regarding their ionization energies.

- **Aluminum (Al):** Electronic configuration is 1s² 2s² 2p⁶ 3s² 3p¹.
- **Phosphorus (P):** Electronic configuration is 1s² 2s² 2p⁶ 3s² 3p³.

When we consider the removal of one electron:
- **Al → Al⁺:** 1s² 2s² 2p⁶ 3s² 3p⁰.
- **P → P⁺:** 1s² 2s² 2p⁶ 3s² 3p².

Phosphorus has a higher ionization energy than aluminum because it has more electrons in the p subshell. Thus, this statement is also correct.

### Step 3: Analyze Statement C
**Statement C:** The first ionization energy of aluminum is the same as that of gallium.

- **Gallium (Ga):** Electronic configuration is 1s² 2s² 2p⁶ 3s² 3p¹ 4s² 3d¹⁰.

Gallium has a larger atomic size compared to aluminum due to the presence of additional electron shells. Therefore, the ionization energy of gallium is less than that of aluminum. This statement is incorrect.

### Step 4: Analyze Statement D
**Statement D:** Comparison of the second ionization energy of Boron and Carbon.

- **Boron (B):** Electronic configuration is 1s² 2s² 2p¹.
- **Carbon (C):** Electronic configuration is 1s² 2s² 2p².

The second ionization energy involves removing an electron from a stable configuration:
- **B → B²⁺:** 1s² 2s² (removal of 2 electrons).
- **C → C²⁺:** 1s² 2s² 2p⁰ (removal of 2 electrons).

Carbon has a higher second ionization energy than boron because it has a higher nuclear charge and a more stable electronic configuration. Thus, this statement is correct.

### Conclusion
The incorrect statement is **Statement C**: "The first ionization energy of aluminum is the same as that of gallium."