# Why are metallic compounds insoluble in water?

Metallic compounds are not pure metals. They are compounds that contain a metal and a nonmetal, which are generally ionic compounds. In an ionic compound, a metal forms an ionic bond with a nonmetal, such as sodium chloride, $\text{NaCl}$, which consists of the metal sodium and the nonmetal chlorine. A metallic compound can also consist of a metal bonded to a polyatomic ion, such as calcium carbonate, $\text{CaCO"_3}$, which consists of the metal calcium bonded to the polyatomic carbonate ion, $\text{CO"_3^(2-)}$.
If you look up the previous two examples, $\text{NaCl}$ and $\text{CaCO"_3}$, you will note that $\text{NaCl}$ is soluble in water, whereas $\text{CaCO"_3}$ is not since $\text{Ca}$ is an alkaline earth metal, not an alkali metal.