Which of the following statements is incorrect ?

Options

A. The ionization potential of nitrogen is greater than of oxygen
B. The electron affinity of fluorine is greater than of chlorine .
C. The ionization potential of Mg is greater than aluminium
D. The electronegativity of fluorine is greater than that of chlorine

Answer

To solve the question "Which of the following statements is incorrect?", we will analyze each of the statements provided in the options.

### Step-by-Step Solution:

1. **Statement 1: The ionization potential of nitrogen is greater than that of oxygen.**
- **Analysis:**
- Ionization potential (or ionization energy) is the energy required to remove an electron from an atom in its gaseous state.
- Nitrogen (atomic number 7) has the electronic configuration of 1s² 2s² 2p³, while oxygen (atomic number 8) has the electronic configuration of 1s² 2s² 2p⁴.
- Nitrogen has a half-filled 2p subshell, which provides extra stability. Thus, it is harder to remove an electron from nitrogen than from oxygen.
- **Conclusion:** This statement is **true**.

2. **Statement 2: The electron affinity of chlorine is greater than that of fluorine.**
- **Analysis:**
- Electron affinity is the energy change when an electron is added to a neutral atom.
- Fluorine (atomic number 9) has a smaller atomic size compared to chlorine (atomic number 17). Although fluorine is more electronegative, its small size leads to significant electron-electron repulsion when an additional electron is added.
- Chlorine, being larger, can accommodate an additional electron more easily, hence has a higher electron affinity.
- **Conclusion:** This statement is **incorrect**.

3. **Statement 3: The ionization potential of magnesium is greater than that of aluminum.**
- **Analysis:**
- Magnesium (atomic number 12) has the electronic configuration of 1s² 2s² 2p⁶ 3s², while aluminum (atomic number 13) has the configuration of 1s² 2s² 2p⁶ 3s² 3p¹.
- Magnesium has a completely filled 3s subshell, which provides extra stability, making it harder to remove an electron compared to aluminum.
- **Conclusion:** This statement is **true**.

4. **Statement 4: The electronegativity of fluorine is greater than that of chlorine.**
- **Analysis:**
- Electronegativity is the tendency of an atom to attract electrons in a bond.
- Fluorine is the most electronegative element due to its small size and high effective nuclear charge, making it more effective at attracting electrons compared to chlorine.
- **Conclusion:** This statement is **true**.

### Final Answer:
The incorrect statement is **Statement 2: The electron affinity of chlorine is greater than that of fluorine.**