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Within each pair of element F & Cl s & s...

Within each pair of element F & Cl s & se, and Li & Na , respectively , the elements that release more energy upon electron gain are

A

Cl , S and Li

B

F, S and Li

C

Cl , Se and Na

D

F, Se and Na

Text Solution

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The correct Answer is:
To determine which element releases more energy upon gaining an electron within the pairs F & Cl, S & Se, and Li & Na, we need to analyze the electron affinity of each element. ### Step-by-Step Solution: 1. **Understanding Electron Affinity**: - Electron affinity is the amount of energy released when an electron is added to a neutral atom. Higher electron affinity means more energy is released upon gaining an electron. 2. **Analyzing the First Pair (F & Cl)**: - Fluorine (F) and Chlorine (Cl) are both halogens. - Generally, as we move down the group in the periodic table, electron affinity decreases due to the increase in atomic size and the corresponding decrease in effective nuclear charge experienced by the added electron. - Although F is more electronegative than Cl, it has a smaller atomic radius, leading to increased electron-electron repulsion when an electron is added. Thus, Cl has a higher electron affinity than F. - **Conclusion for Pair 1**: Cl releases more energy upon gaining an electron than F. 3. **Analyzing the Second Pair (S & Se)**: - Sulfur (S) and Selenium (Se) are in the same group (Group 16). - As we move down the group from S to Se, the size of the atom increases, which generally leads to a decrease in electron affinity. - Therefore, sulfur (S) has a higher electron affinity than selenium (Se). - **Conclusion for Pair 2**: S releases more energy upon gaining an electron than Se. 4. **Analyzing the Third Pair (Li & Na)**: - Lithium (Li) and Sodium (Na) are both alkali metals (Group 1). - Similar to the previous pairs, as we move down the group from Li to Na, the atomic size increases, leading to a decrease in electron affinity. - Thus, lithium (Li) has a higher electron affinity than sodium (Na). - **Conclusion for Pair 3**: Li releases more energy upon gaining an electron than Na. 5. **Final Summary**: - For the pairs: - F & Cl: Cl releases more energy. - S & Se: S releases more energy. - Li & Na: Li releases more energy. - Therefore, the elements that release more energy upon electron gain are Cl, S, and Li, respectively. ### Final Answer: The elements that release more energy upon electron gain are: - Cl (for F & Cl) - S (for S & Se) - Li (for Li & Na)
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