Arrange N, O and S in order of decreasing electron affinity:

Options

A. SgtOgtN
B. OgtSgtN
C. NgtOgtS
D. SgtNgtO

Answer

To arrange nitrogen (N), oxygen (O), and sulfur (S) in order of decreasing electron affinity, we will follow these steps:

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

### Step 2: Identify the General Trend
- **Across a Period**: As you move from left to right across a period, electron affinity generally increases. This is because the atomic size decreases and the effective nuclear charge increases, making it easier for the atom to attract an additional electron.
- **Down a Group**: As you move down a group, electron affinity generally decreases. This is due to the increase in atomic size and the distance of the outermost electrons from the nucleus, which reduces the attraction.

### Step 3: Analyze the Elements
- **Nitrogen (N)**: Located in Group 15, it has a relatively low electron affinity because it has a half-filled p subshell, which is stable.
- **Oxygen (O)**: Located in Group 16, it has a higher electron affinity than nitrogen, but due to electron-electron repulsion in its small 2p subshell, its electron affinity is less than that of sulfur.
- **Sulfur (S)**: Located in Group 16, below oxygen, it has a higher electron affinity than oxygen because it has a larger atomic size, which reduces electron-electron repulsion compared to oxygen.

### Step 4: Arrange the Elements
Based on the analysis:
1. **Sulfur (S)** has the highest electron affinity.
2. **Oxygen (O)** has a lower electron affinity than sulfur but higher than nitrogen.
3. **Nitrogen (N)** has the lowest electron affinity.

Thus, the order of decreasing electron affinity is:
**S > O > N**

### Final Answer
The correct order of decreasing electron affinity for N, O, and S is **S > O > N**.

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