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 given statements is incorrect, let's analyze each statement one by one.

### Statement A:
**The second ionization energy of sulfur is greater than that of chlorine.**

- **Analysis**:
- Sulfur (S) has the electronic configuration of [Ne]3s²3p⁴, and chlorine (Cl) has [Ne]3s²3p⁵.
- When we remove the second electron from sulfur, it becomes S²⁺, which has a half-filled p subshell (3p³), making it more stable.
- For chlorine, removing the second electron (after the first one) leads to Cl⁺, which is less stable than S²⁺.
- Therefore, the second ionization energy of sulfur is indeed greater than that of chlorine.

**Conclusion**: Statement A is **correct**.

### Statement B:
**The third ionization energy of phosphorus is greater than that of aluminum.**

- **Analysis**:
- Phosphorus (P) has the electronic configuration of [Ne]3s²3p³, while aluminum (Al) has [Ne]3s²3p¹.
- Removing the third electron from phosphorus will lead to P³⁺, which is less stable compared to Al³⁺.
- The third ionization energy of phosphorus is higher because it involves removing an electron from a half-filled p subshell, which is relatively stable.
- Therefore, the third ionization energy of phosphorus is indeed greater than that of aluminum.

**Conclusion**: Statement B is **correct**.

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

- **Analysis**:
- Aluminum (Al) has the electronic configuration of [Ne]3s²3p¹, and gallium (Ga) has [Ar]3d¹⁰4s²4p¹.
- Ionization energy generally decreases down a group, but gallium has a higher effective nuclear charge due to the presence of d-electrons, which leads to a higher ionization energy than aluminum.
- Therefore, the first ionization energy of aluminum is not approximately the same as that of gallium; gallium has a higher ionization energy.

**Conclusion**: Statement C is **incorrect**.

### Statement D:
**The second ionization energy of boron is greater than that of carbon.**

- **Analysis**:
- Boron (B) has the electronic configuration of [He]2s²2p¹, and carbon (C) has [He]2s²2p².
- The removal of the second electron from boron leads to a stable configuration (B²⁺ is stable), while removing a second electron from carbon leads to C⁺, which is less stable.
- Therefore, the second ionization energy of boron is indeed greater than that of carbon.

**Conclusion**: Statement D is **correct**.

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

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