Order of Electron affinity of the elements or ions shown correctly?

Options

A. `S gt O^(-)`
B. `P gt N^(-)`
C. `O^(-) gt S^(-)`
D. `N^(-) gt P`

Answer

To determine the correct order of electron affinity for the elements or ions provided, we need to analyze the electron affinity trends based on their atomic structure and size. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand Electron Affinity
Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gas phase. A more negative electron affinity indicates a greater tendency to accept an electron.

### Step 2: Compare Elements in the Same Period
- **Oxygen (O) vs. Sulfur (S)**:
- Oxygen has a smaller atomic size compared to sulfur.
- When oxygen accepts an electron to form O⁻, it experiences increased electron-electron repulsion due to its small size and already filled valence shell (6 electrons). This makes the process endothermic (requires energy).
- In contrast, sulfur, being larger, can accommodate an additional electron more easily, making the formation of S⁻ more favorable.

### Step 3: Compare Elements in Different Periods
- **Nitrogen (N) vs. Phosphorus (P)**:
- Nitrogen is in the second period, while phosphorus is in the third period.
- Similar to the previous comparison, nitrogen has a smaller atomic size, which makes it harder to add an electron compared to phosphorus.
- Phosphorus can accept an electron more easily due to its larger size and availability of more vacant orbitals.

### Step 4: Establish the Order of Electron Affinity
Based on the analysis:
- For the comparison of O and S: **S⁻ > O⁻** (Sulfur has a higher electron affinity than oxygen)
- For the comparison of N and P: **P⁻ > N⁻** (Phosphorus has a higher electron affinity than nitrogen)

### Step 5: Conclusion
The correct order of electron affinity for the elements discussed can be summarized as:
- **S⁻ > O⁻** and **P⁻ > N⁻**

### Final Answer
The order of electron affinity of the elements or ions is:
1. S⁻ > O⁻
2. P⁻ > N⁻