Energy is released when an electron is added to neutral isolated gaseous atom in its ground state to give monoanion and this is
known as `EA`, or `Delta_(eg)H_(1)^(ɵ)`. The greater the amount of energy
released the greater is the `EA`. `EA` is expressed in `eV "atom"^(-1)` or `kcal or kJ mol^(-1)`.
Select the correct statement (more than one correct)

Options

A. `Delta_(eg)H^(ɵ)` of noble gases have large positive values.
B. `Delta_(eg)H^(ɵ)` of noble gases have large negative values.
C. `Delta_(eg)H^(ɵ)` of helium `(He)` is the lowest of all the noble gases.
D. `Delta_(eg)H^(ɵ)` of `Ar` is lower than that of `Ne`.

Answer

To solve the question regarding electron affinity (EA) and to select the correct statements, we will analyze each statement based on the principles of electron gain enthalpy.

### Step-by-Step Solution:

1. **Understanding Electron Affinity (EA)**:
- Electron affinity is the energy change that occurs when an electron is added to a neutral atom in its gaseous state to form a monoanion. A more negative EA value indicates a greater tendency of an atom to accept an electron.

2. **Evaluating the Statements**:
- **Statement 1**: "Electron gain enthalpy of noble gases have large positive values."
- **Analysis**: This statement is correct. Noble gases have a stable electronic configuration and do not favorably accept additional electrons. Therefore, energy is required to add an electron, resulting in a positive electron gain enthalpy.

- **Statement 2**: "Electron gain enthalpy of noble gases are large."
- **Analysis**: This statement is incorrect. While noble gases have positive values for electron gain enthalpy, they are not considered "large" in the context of electron gain enthalpy compared to other elements that readily accept electrons.

- **Statement 3**: "Electron gain enthalpy of helium is lowest of all the noble gases."
- **Analysis**: This statement is correct. Helium, being the smallest noble gas, has a relatively high tendency to accept an electron compared to other noble gases, resulting in it having the least positive electron gain enthalpy.

- **Statement 4**: "Electron gain enthalpy of argon is lower than that of neon."
- **Analysis**: This statement is correct. As we move down the group in the periodic table, the size of the atoms increases, which generally leads to a decrease in the electron gain enthalpy. Therefore, argon has a lower electron gain enthalpy than neon.

3. **Conclusion**:
- The correct statements are **1, 3, and 4**.

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