To see all my Chemistry videos, check out http://socratic.org/chemistry How can you tell the difference between compounds that are ionic and molecular (also known as covalent)? It has to do with the elements that make them up: ionic compounds are made of metals and nonmetals, and molecular (or covalent) compounds are made of nonmetals. We'll learn how they bond differently: in covalent compounds, the atoms share electrons, and in ion compounds, atoms steal electrons and then opposite charges attract. Ionic and molecular (covalent) compounds also look different at the microscopic level: covalent and molecular compounds exist in molecules, while ionic compounds are organized in lattice structures.