Which of the following atom should have the highest negative first electron gain enthalpy ?

Options

A. F
B. O
C. N
D. C

Explanation

To determine which atom has the highest negative first electron gain enthalpy, we need to analyze the electron gain enthalpy of various elements, particularly focusing on the halogens. Here’s a step-by-step solution:

### Step 1: Understand Electron Gain Enthalpy
Electron gain enthalpy is 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 Relevant Elements
The elements that typically have high negative electron gain enthalpy values are the halogens (Group 17 elements) such as fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).

### Step 3: Compare the Halogens
- **Fluorine (F)**: Being the smallest halogen, it has a high effective nuclear charge and a small atomic radius, which allows it to attract an additional electron more effectively.
- **Chlorine (Cl)**: Larger than fluorine, and while it also has a high electron gain enthalpy, it is not as negative as that of fluorine.
- **Bromine (Br)** and **Iodine (I)**: These are even larger and have lower electron gain enthalpy values compared to fluorine and chlorine.

### Step 4: Conclusion
Among the halogens, fluorine has the highest negative first electron gain enthalpy due to its small size and high electronegativity, making it very effective at gaining an electron.

### Final Answer
Fluorine (F) has the highest negative first electron gain enthalpy.

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