Within each pair of elements F & Cl, S & Se, and Li & Na respectively, the elements that release more energy upon an electron gain are:
Correct answer: B. Cl, S and Li
- A. F, S and Li
- B. Cl, S and Li
- C. Cl, Se and Na
- D. F, Se and Na
Explanation
In the periodic table, electron affinity generally increases across a period and decreases down a group. Although fluorine is more electronegative, chlorine actually releases more energy when gaining an electron due to reduced electron repulsion compared to fluorine. Sulfur, being in the same group but a period above selenium, releases more energy due to its smaller atomic size. Similarly, lithium, being in the same group but a period above sodium, releases more energy when gaining an electron because of its smaller atomic size, leading to a stronger attraction to the newly added electron. Thus, the correct answer is Cl, S, and Li.
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About Periodic Properties and Trends
Periodic properties arise from electron configuration and effective nuclear charge, producing trends in atomic and ionic radius, ionization energy, electron affinity, electronegativity, metallic character and reactivity. Comparisons run across periods and down groups, with attention to common exceptions. The topic also relates these trends to the behavior of s-block and p-block elements.
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