2.2.1: Trends in Size (Problems)

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PROBLEM \(\PageIndex{1}\)

Based on their positions in the periodic table, predict which has the smallest atomic radius: Mg, Sr, Si, Cl, I.

Answer: Cl

PROBLEM \(\PageIndex{2}\)

Based on their positions in the periodic table, predict which has the largest atomic radius: Li, Rb, N, F, I.

Answer: Rb

PROBLEM \(\PageIndex{3}\)

Based on their positions in the periodic table, list the following atoms in order of increasing radius: Cs, Ca, Rb, Mg

Answer: Mg < Ca < Rb < Cs

PROBLEM \(\PageIndex{4}\)

Based on their positions in the periodic table, list the following atoms in order of increasing radius: Sr, Cl, Ca, Si.

Answer: Cl < Si < Ca < Sr

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PROBLEM \(\PageIndex{5}\)

Based on their positions in the periodic table, list the following ions in order of increasing radius: K⁺, Ca²⁺, Al³⁺, Si⁴⁺.

Answer: Si⁴⁺ < Al³⁺ < Ca²⁺ < K⁺

PROBLEM \(\PageIndex{6}\)

List the following ions in order of increasing radius: Br^–, Li⁺, Te^2–, Mg²⁺.

Answer: Li⁺<Mg²⁺ < Br^–< Te^2–

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PROBLEM \(\PageIndex{7}\)

Which atom and/or ion is (are) isoelectronic with Br⁺: Se²⁺, Se, As^–, Kr, Ga³⁺, Cl^–?

Answer: Se, As⁻

PROBLEM \(\PageIndex{8}\)

Which of the following atoms and ions is (are) isoelectronic with S²⁺: Si⁴⁺, Cl³⁺, Ar, As³⁺, Si, Al³⁺?

Answer: Si, Cl³⁺

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PROBLEM \(\PageIndex{9}\)

Compare both the numbers of protons and electrons present in each to rank the following ions in order of increasing radius: As^3–, Br^–, K⁺, Mg²⁺.

Answer: Mg²⁺ < K⁺ < Br^– < As^3–

PROBLEM \(\PageIndex{10}\)

The ionic radii of the ions S^2–, Cl^–, and K⁺ are 184, 181, 138 pm respectively. Explain why these ions have different sizes even though they contain the same number of electrons.

Answer: They have different numbers of protons, which determines their size.

Contributors

Paul Flowers (University of North Carolina - Pembroke), Klaus Theopold (University of Delaware) and Richard Langley (Stephen F. Austin State University) with contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at http://cnx.org/contents/85abf193-2bd...a7ac8df6@9.110).
Adelaide Clark, Oregon Institute of Technology

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