Which of the following statements are correct?

Options

A. The electron affinity of Si is greater than that of C.
B. BeO is amphoteric while `B_2 O_3` is acidic.
C. The ionization energy of Ti is less than that of Al.
D. The ionization energy of elements of Cu-group is less than that of the respective elements of Zn-group.

Answer

To determine which statements are correct, we will analyze each statement one by one based on the principles of chemistry, particularly focusing on electron affinity, acidity, and ionization energy.

### Step-by-Step Solution:

1. **Analyze the first statement: "The electron affinity of silicon is greater than that of carbon."**
- **Definition**: Electron affinity is the amount of energy released when an electron is added to a neutral atom.
- **Comparison**: Carbon (C) has a smaller atomic size compared to silicon (Si). When an electron is added to carbon, the increased electron-electron repulsion due to its smaller size makes it less favorable for carbon to gain an electron compared to silicon.
- **Conclusion**: Therefore, the electron affinity of silicon is indeed greater than that of carbon.
- **Result**: This statement is **correct**.

2. **Analyze the second statement: "Beryllium oxide is amphoteric while B2O3 is acidic."**
- **Beryllium Oxide (BeO)**: BeO can react with both acids and bases, which makes it amphoteric.
- **Boron Trioxide (B2O3)**: In B2O3, boron has an oxidation state of +3. It tends to accept electrons, which is characteristic of acidic oxides.
- **Conclusion**: Both parts of this statement are true.
- **Result**: This statement is **correct**.

3. **Analyze the third statement: "The ionization energy of titanium is less than that of aluminium."**
- **Electron Configuration**: Titanium (Ti) has the configuration [Ar] 3d² 4s², while Aluminium (Al) has [Ne] 3s² 3p¹.
- **Ionization Energy Trend**: Aluminium has a relatively stable configuration after losing one electron, while titanium has a more complex electron configuration with d-electrons that experience less shielding. This results in titanium having a higher ionization energy than aluminium.
- **Conclusion**: The statement is incorrect.
- **Result**: This statement is **wrong**.

4. **Analyze the fourth statement: "The ionization energy of the copper group is less than that of the respective zinc group."**
- **Electron Configuration**: Copper (Cu) has the configuration [Ar] 3d¹⁰ 4s¹, while Zinc (Zn) has [Ar] 3d¹⁰ 4s².
- **Stability**: Zinc has a stable electron configuration (fully filled 4s and 3d orbitals), making it harder to remove an electron compared to copper, which has a less stable configuration.
- **Conclusion**: Therefore, the ionization energy of the copper group is indeed less than that of the zinc group.
- **Result**: This statement is **correct**.

### Final Conclusion:
The correct statements are:
- The electron affinity of silicon is greater than that of carbon.
- Beryllium oxide is amphoteric while B2O3 is acidic.
- The ionization energy of the copper group is less than that of the respective zinc group.

Thus, the correct options are 1, 2, and 4.

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