Chapter 7.5, Problem 2CP

Which of the following pairs are isoelectronic with each other? (Select all that apply.)

a)

${\text{Ca}}^{\text{2+}}{\text{and Sr}}^{\text{2+}}$

b)

${\text{O}}^{\text{2–}}{\text{ and Mg}}^{\text{2+}}$

c)

${\text{I}}^{\text{-}} \text{ and Kr}$

d)

${\text{S}}^{2-}{\text{ and Cl}}^{-}$

e)

${\text{He and H}}^{\text{+}}$