Which of the following represents the correct order of ionic radii?
Correct answer: A. Li+ < Na+ < K+ < Rb+
- A. Li+ < Na+ < K+ < Rb+
- B. Li+ > Na+ > K+ > Rb+
- C. Li+ = Na+ = K+ = Rb+
- D. Rb+ > Na+ > K+ > Li+.
Explanation
The correct order of ionic radii for alkali metal ions is Li+ < Na+ < K+ < Rb+. This is because as you move down Group 1 in the periodic table, each successive element has an additional electron shell, thereby increasing the size of the ion. Option A correctly reflects this trend. Options B and D incorrectly suggest that ionic radii decrease or are incorrectly ordered, while Option C incorrectly assumes that all ions have equal radii, which is not the case.
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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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