# 2.2.1: Trends in Size (Problems)

PROBLEM $$\PageIndex{1}$$

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

Cl

PROBLEM $$\PageIndex{2}$$

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

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

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.

Cl < Si < Ca < Sr

PROBLEM $$\PageIndex{5}$$

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

Si4+ < Al3+ < Ca2+ < K+

PROBLEM $$\PageIndex{6}$$

List the following ions in order of increasing radius: Br, Li+, Te2–, Mg2+.

Li+ < Mg2+ < Br< Te2–

PROBLEM $$\PageIndex{7}$$

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

Se, As

PROBLEM $$\PageIndex{8}$$

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

Si, Cl3+

PROBLEM $$\PageIndex{9}$$

Compare both the numbers of protons and electrons present in each to rank the following ions in order of increasing radius: As3–, Br, K+, Mg2+.

Mg2+ < K+ < Br < As3–

PROBLEM $$\PageIndex{10}$$

The ionic radii of the ions S2–, 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.