To determine which of the pairs is most likely to form an ionic bond, we need to consider the electronegativity and the type of elements involved.
Ionic bonds typically form between metals and nonmetals, where the metal donates electrons and the nonmetal accepts electrons.
- C and O: Both carbon (C) and oxygen (O) are nonmetals; they are more likely to form covalent bonds.
- K and Cl: Potassium (K) is a metal, and chlorine (Cl) is a nonmetal. This pair is likely to form an ionic bond.
- K and Ca: Both potassium (K) and calcium (Ca) are metals, so they are unlikely to form an ionic bond.
- S and Cl: Both sulfur (S) and chlorine (Cl) are nonmetals; they are more likely to form covalent bonds.
Based on this analysis, the pair K and Cl is most likely to form an ionic bond.