Within each pair of elements F and Cl, S and Se, and Li and Na respectively, the elements that release more energy upon an electron gain are:

• A) F, S and Li
• B) Cl, S and Li
• C) Cl, Se and Na

To determine which elements release more energy upon gaining an electron, we need to consider their positions in the periodic table and their electronegativities.

Energy Release Upon Electron Gain

When an atom gains an electron, it releases energy, known as electron affinity. Generally, elements that are more electronegative tend to have higher electron affinities.

Analyzing the Pairs

• F (Fluorine) vs. Cl (Chlorine): Fluorine has a higher electron affinity than chlorine.
• S (Sulfur) vs. Se (Selenium): Sulfur has a higher electron affinity than selenium.
• Li (Lithium) vs. Na (Sodium): Lithium has a higher electron affinity than sodium.

Conclusion on Energy Release

Based on the analysis, the elements that release more energy upon gaining an electron are:

F, S, and Li

Thus, the correct answer is A) F, S, and Li.