Answer:
KCl
Explanation:
Ionic compounds are formed between atoms with very different electronegativity (EN) values. The elements with the highest EN values are on the top-right of the periodic table.
Ionic compounds are also generally between a metal and nonmetal. Nonmetals are located in the p-block (the right) of the periodic table and metals are pretty much everywhere else.
That being said, water (H₂O), CO, and CO₂ contain elements that have too similar of EN values to ionically bond.
However, the elements in KCl have different enough EN values to undergo ionic bonding by donating/receiving electrons from each other.
