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)`.
`EA` values of `N` and `P` are exceptionally low, because

Options

A. Both `N` and `P` have half-filled `p`-orbitals in the valence shell.
B. The atom is more stable than the corresponding anoin.
C. The electronic configuration of the anoin `N^(ɵ)` and `P^(ɵ)` is relatively more stable than the corresponding atom.
D. Both (b) and C.

Answer

To understand why the electron affinity (EA) values of nitrogen (N) and phosphorus (P) are exceptionally low, we can break down the explanation into a series of logical steps:

### Step-by-Step Solution:

1. **Identify the Group of Elements**:
- Nitrogen (N) and phosphorus (P) belong to Group 15 of the periodic table. This group is characterized by having five valence electrons.

2. **Electronic Configuration**:
- The electronic configuration of nitrogen is \(1s^2 2s^2 2p^3\) and for phosphorus, it is \(1s^2 2s^2 2p^6 3s^2 3p^3\).
- Both elements have a half-filled p subshell (2p^3 for N and 3p^3 for P), which contributes to their stability.

3. **Stability of Half-Filled Orbitals**:
- Half-filled and fully filled subshells are particularly stable due to symmetry and exchange energy.
- In the case of nitrogen, adding an electron would change its configuration from \(2p^3\) to \(2p^4\), which is less stable. Similarly, phosphorus would go from \(3p^3\) to \(3p^4\).

4. **Energy Consideration**:
- When an electron is added to a stable half-filled subshell, the system moves from a more stable state to a less stable state.
- This results in less energy being released during the addition of the electron, leading to a low electron affinity.

5. **Conclusion**:
- Therefore, the low electron affinity values of nitrogen and phosphorus can be attributed to their stable half-filled p orbitals. Adding an electron disrupts this stability, resulting in a lower tendency to gain an electron.

### Final Answer:
The electron affinity values of nitrogen and phosphorus are exceptionally low because both elements have half-filled p orbitals, which are stable. Adding an electron to these stable configurations results in a less stable anion, thus lowering the energy released during the process.