The set representing the correct order of first ionization energy is:
Correct answer: D. Both (b) and (c).
- A. K > Na > Li
- B. Be > Mg > Ca
- C. N > P > As
- D. Both (b) and (c).
Explanation
Ionization energy generally decreases as you move down a group in the periodic table because the outermost electrons are farther from the nucleus and are less tightly held due to increased atomic size. Option A is incorrect because it suggests potassium has a higher ionization energy than sodium and lithium, which contradicts the trend of decreasing ionization energy down a group. Option B is correct as Be > Mg > Ca follows the trend of decreasing ionization energy down the group. Option C is correct as N > P > As also follows this trend. Therefore, Option D is the correct choice as it correctly identifies that both orders in Options B and C follow the trend of ionization energy decreasing down a group.
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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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