2.  Ion – atom or group of atoms that has an electric charge  Ionic bonds form when atoms gain or lose electrons.  When an atom loses an electron, it becomes a positive ion. Ex. Li+  When an atom gains an electron, it becomes a negative ion. Ex. Cl-

3.  A compound that consists of ions is called an ionic compound.  The name of the positive ion comes first, followed by the name of the negative ion. (This means metal before nonmetal or metalloid, left before right)

4.  A chemical formula is a combination of symbols that shows the ratio of elements in a compound. Ex. CO = 1 carbon & 1 oxygen  A subscript tells you the ratio of elements in the compound. Ex. CO 2 (2 = the subscript)  If there is no subscript (number), the number is understood to be 1.

5.  The magic number is 2 and 8.  All atoms will lose, gain, or share electrons to get to the magic number.  Ionic bonds generally occur between metals and nonmetals (or different sides of the periodic table).  Example: Cl has 7 electrons H has 1 electron HCl has 8 so the two combine