Which of the following elements have the most negative electron gain enthalpies corresponding to the largest release of enegry?

Options

A. Group `2` elements
B. Group`16`elements
C. Group `17`elements
D. Group`18`elements

Explanation

To determine which of the given groups of elements has the most negative electron gain enthalpy, we can follow these steps:

### Step-by-Step Solution

1. **Understand Electron Gain Enthalpy**:
- Electron gain enthalpy refers to the energy change when an electron is added to a neutral atom in the gas phase. A more negative value indicates a greater release of energy, meaning the atom becomes more stable after gaining an electron.

2. **Identify the Groups**:
- The options provided are Group 2, Group 16, Group 17, and Group 18. We need to analyze the electron gain enthalpy for elements in each of these groups.

3. **Analyze Group 2 Elements**:
- Group 2 elements (alkaline earth metals) have the electron configuration of Ns². They are already stable and do not favorably gain electrons. Therefore, their electron gain enthalpy is positive, indicating energy is absorbed when an electron is added.

4. **Analyze Group 16 Elements**:
- Group 16 elements (chalcogens) typically gain two electrons. The first electron gain is exothermic (negative enthalpy), but the second electron gain is endothermic (positive enthalpy). Thus, the overall electron gain enthalpy is not very negative.

5. **Analyze Group 17 Elements**:
- Group 17 elements (halogens) are highly electronegative and readily gain one electron to achieve a noble gas configuration. For example, chlorine (Cl) gains an electron to become Cl⁻, achieving the stable electron configuration of argon. This process releases a significant amount of energy, resulting in a very negative electron gain enthalpy.

6. **Analyze Group 18 Elements**:
- Group 18 elements (noble gases) have a complete valence shell (Ns²Np⁶) and are very stable. Adding an electron to these elements requires energy, making their electron gain enthalpy positive.

7. **Conclusion**:
- Based on the analysis, Group 17 elements have the most negative electron gain enthalpy because they release the most energy upon gaining an electron.

### Final Answer:
**Group 17 elements have the most negative electron gain enthalpies corresponding to the largest release of energy.**

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