## Chemistry and Chemical Reactivity (9th Edition)

$CaO$
In NaCl, one electron is exchanged, and in CaO, two ($Ca^{2+}, O^{2-}$) are exchanged. From Couloumb's Law: $F=-k\frac{q_1q_2}{d^2}$ Since $q_1$ and $q_2$ are greater for Calcium and Oxygen than for Sodium and Chlorine, the attractive force is greater for CaO.