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 a"atom"^(-1)` or `kcal or K\kJ mol^(-1)`.
Select the correct statements (more than one correct)

Options

A. `EA` and `Delta_(eg)H_(1)^(ɵ)` of an atom of element have same magnitude
B. `Delta_(eg)H_(1)^(ɵ)` of `Al gt B`
C. `Delta_(eg)H_(1)^(ɵ)`of `P gt N`
D. `Delta_(eg)H_(1)^(ɵ)` of `S gt O`

Explanation

To solve the question regarding electron affinity (EA) and to select the correct statements, we can follow these steps:

### Step 1: Understand Electron Affinity (EA)
Electron affinity is defined as the amount of energy released when an electron is added to a neutral isolated gaseous atom in its ground state to form a monoanion. The greater the energy released, the greater the electron affinity.

### Step 2: Analyze the First Statement
The first statement claims that "electron affinity and electron gain enthalpy of an atom of an element have the same magnitude."
- **Analysis**: Electron affinity is usually expressed as a negative value because energy is released when an electron is added. Electron gain enthalpy is also negative for the same reason. Therefore, they have the same magnitude but opposite signs.
- **Conclusion**: This statement is **correct**.

### Step 3: Analyze the Second Statement
The second statement suggests that "electron gain enthalpy of aluminum should be greater than that of boron."
- **Analysis**: Aluminum (Al) is larger than boron (B) in atomic size. A larger atomic size means that the outer electrons are further from the nucleus, which allows for easier addition of an electron. Thus, aluminum can accommodate an additional electron more easily than boron.
- **Conclusion**: This statement is **correct**.

### Step 4: Analyze the Third Statement
The third statement states that "electron gain enthalpy of phosphorus is greater than that of nitrogen."
- **Analysis**: Phosphorus (P) is larger than nitrogen (N). Similar to the previous analysis, the larger size of phosphorus allows it to accommodate an additional electron more easily than nitrogen.
- **Conclusion**: This statement is **correct**.

### Step 5: Analyze the Fourth Statement
The fourth statement claims that "electron gain enthalpy of sulfur is greater than that of oxygen."
- **Analysis**: Sulfur (S) is larger than oxygen (O). Therefore, sulfur can also accommodate an additional electron more easily than oxygen.
- **Conclusion**: This statement is **correct**.

### Final Conclusion
All the statements provided in the question are correct.

### Summary of Correct Statements:
1. Electron affinity and electron gain enthalpy of an atom of an element have the same magnitude.
2. Electron gain enthalpy of aluminum is greater than that of boron.
3. Electron gain enthalpy of phosphorus is greater than that of nitrogen.
4. Electron gain enthalpy of sulfur is greater than that of oxygen.