Which of the following statement regarding halogens is/are correct?

Options

A. Ionization energy decreases with increase in atomic number
B. electronegativity decreases with increase in atomic number
C. Electron affinity decreases with increase in atomic number
D. Enthalpy of fusion increses with increase in atomic number

Answer

To determine which statements regarding halogens are correct, we will analyze each statement based on periodic trends.

### Step 1: Analyze Ionization Energy
- **Statement 1**: Ionization energy decreases with an increase in atomic number.
- **Explanation**: As we move down the group of halogens (from fluorine to iodine), the atomic size increases due to the addition of electron shells. This increase in size leads to a weaker attraction between the nucleus and the outermost electrons, making it easier to remove an electron. Thus, the ionization energy decreases.
- **Conclusion**: This statement is **correct**.

### Step 2: Analyze Electronegativity
- **Statement 2**: Electronegativity decreases with an increase in atomic number.
- **Explanation**: Electronegativity is the tendency of an atom to attract electrons in a bond. As the atomic number increases down the group, the size of the atoms increases, which results in a decrease in electronegativity. This is because the increased distance between the nucleus and the valence electrons reduces the effective nuclear charge felt by the outer electrons.
- **Conclusion**: This statement is **correct**.

### Step 3: Analyze Electron Affinity
- **Statement 3**: Electron affinity decreases with an increase in atomic number.
- **Explanation**: Electron affinity is the energy change when an electron is added to a neutral atom. However, the trend in electron affinity for halogens does not follow a simple pattern. For example, chlorine has a higher electron affinity than fluorine, which contradicts the idea that it decreases with atomic number. Therefore, this statement is not universally true.
- **Conclusion**: This statement is **incorrect**.

### Step 4: Analyze Enthalpy of Fusion
- **Statement 4**: Enthalpy of fusion increases with an increase in atomic number.
- **Explanation**: The enthalpy of fusion refers to the energy required to change a substance from solid to liquid at its melting point. For halogens, as we move down the group, the molecular size and the number of electrons increase, leading to stronger van der Waals forces. This generally results in a higher enthalpy of fusion for heavier halogens compared to lighter ones.
- **Conclusion**: This statement is **correct**.

### Final Summary
- **Correct Statements**:
- Statement 1: Correct
- Statement 2: Correct
- Statement 3: Incorrect
- Statement 4: Correct

### Overall Conclusion
The correct statements regarding halogens are statements 1, 2, and 4.

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