Which of the following elements is expected to have highest electron affinity ?

Options

A. `1s^(2)2s^(2)2p^(6) 3s^(2)3p^(5)`
B. `1s^(2)2s^(2)2p^(3)`
C. `1s^(2)2s^(2)2p^(4)`
D. `1s^(2)2s^(2)2p^(5)`

Explanation

To determine which of the given elements has the highest electron affinity, we can analyze the electron configurations and the stability of the resulting configurations after gaining an electron. 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. A higher electron affinity means that the atom is more likely to gain an electron and form a negative ion.

### Step 2: Analyze the Given Elements
We will consider the electron configurations of the elements mentioned in the question. Let's assume the elements are Chlorine (Cl), Nitrogen (N), Oxygen (O), and Fluorine (F).

### Step 3: Electron Configuration
- **Chlorine (Cl)**: Atomic number 17
- Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁵
- Chlorine has 5 electrons in its outermost p orbital and can easily gain one more to complete its octet.

- **Nitrogen (N)**: Atomic number 7
- Electron configuration: 1s² 2s² 2p³
- Nitrogen has 3 electrons in its p orbital. Gaining an electron leads to a half-filled configuration, which is less stable compared to chlorine.

- **Oxygen (O)**: Atomic number 8
- Electron configuration: 1s² 2s² 2p⁴
- Oxygen has 4 electrons in its p orbital. While it can gain an electron, the resulting configuration is not as stable as that of chlorine.

- **Fluorine (F)**: Atomic number 9
- Electron configuration: 1s² 2s² 2p⁵
- Fluorine has 5 electrons in its p orbital, similar to chlorine. However, due to its smaller size, the incoming electron experiences repulsion, reducing its affinity.

### Step 4: Compare Electron Affinities
- Chlorine is expected to have the highest electron affinity because:
- It achieves a stable noble gas configuration (Neon) upon gaining an electron.
- The size of chlorine allows for less electron-electron repulsion compared to fluorine.

### Conclusion
Based on the analysis, **Chlorine (Cl)** is expected to have the highest electron affinity among the given elements.

### Final Answer
**Chlorine (Cl)** has the highest electron affinity.

---