Correct order of electron affinity is/are:

Options

A. `S gt O`
B. `Al gt B`
C. `Mg gt Na`
D. `P gt N`

Answer

To determine the correct order of electron affinity among the given elements, we need to analyze the electron affinity trends based on their positions in the periodic table. Here’s a step-by-step breakdown of the reasoning:

### Step 1: Understanding Electron Affinity
- **Definition**: Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gas phase. A higher (more negative) electron affinity means that an atom more readily accepts an electron.

### Step 2: Group Trends
- **Group Trend**: As we move down a group in the periodic table, the size of the atoms increases due to the addition of electron shells. This generally leads to a decrease in electron affinity because the added electron is further from the nucleus and experiences less attraction.

### Step 3: Comparing Elements
- **Sulfur vs. Oxygen**: Both belong to Group 16. Oxygen is smaller than sulfur, making it less able to accommodate an additional electron due to increased electron-electron repulsion in its compact structure. Thus, sulfur has a greater electron affinity than oxygen.

- **Aluminum vs. Boron**: Both belong to Group 13. Boron is smaller than aluminum, so it has a higher electron affinity than aluminum due to the same reasons as above.

- **Magnesium vs. Sodium**: Magnesium is in Group 2 and sodium in Group 1. Sodium is larger than magnesium, which allows it to accept an electron more easily despite magnesium having a higher electronegativity. Thus, sodium has a greater electron affinity than magnesium.

- **Phosphorus vs. Nitrogen**: Both belong to Group 15. Nitrogen is smaller than phosphorus, making it less favorable for nitrogen to accept an additional electron due to repulsion. Therefore, phosphorus has a greater electron affinity than nitrogen.

### Step 4: Summary of Findings
- **Correct Order of Electron Affinity**:
- Sulfur (S) > Oxygen (O)
- Boron (B) > Aluminum (Al)
- Sodium (Na) > Magnesium (Mg)
- Phosphorus (P) > Nitrogen (N)

### Conclusion
Based on the analysis, the correct order of electron affinity is:
- **Sulfur > Oxygen**
- **Boron > Aluminum**
- **Sodium > Magnesium**
- **Phosphorus > Nitrogen**