How do you know if a molcule is an ion

You can tell a ionic bond is between a metal and a nonmetal, so if you usually just look at the periodic table and determine your "molecule" is a ion or not ion.

There is a couple different ways to determine if a bond is ionic or covalent. By definition, an ionic bond is between a metal and a nonmetal, and a covalent bond is between 2 nonmetals. So you usually just look at the periodic table and determine whether your compound is made of a metal/nonmetal or is just 2 nonmetals