Exercise Solutions/Answers

Exercise 1. Use the periodic table to order the following sets of elements in increasing atomic radius:

Exercise 2. Which is larger? Mg²⁺ or Br^–
Br^–
Exercise 3. Order the following ions from smallest to largest.

Se^2-, Sr²⁺, Br^–, Rb⁺

Sr²⁺ < Rb⁺ < Br^– < Se^2-

Exercise 4. The ions and atoms, Ca²⁺, K⁺, S^2-, Cl^–, and Ar, are isoelectronic. Are they different or the same in size? Explain.
These all have the same electron configuration, but they differ in the number of protons. The ones with the greater nuclear charge are smaller. They are all different sizes because of the difference in the number of protons.

Back to Atomic and Ionic Radii