1. *Opposites Attract* Sodium transfers 1 valence electron to chlorine

2. Chemical Formulas (a combination of symbols that show the ratio of elements in a compound) MgCl 2 ------> 1 magnesium, 2 chlorine NaCl -------> 1 sodium, 1 chlorine CaCO 3 -------> __ Calcium, __ Carbon, __ Oxygen NH 4 NO 3 ------> ? ? ? ? Subscripts- The #’s which tell how many elements are in compound *If compound has no subscript, it is understood to be a 1

3. 1. When naming ionic compounds the (+) ion comes first followed by the (-) ion. 2.If the (-) ion is a single element, the end of name changes to –ide. Sodium chloride (NaCl) 3. If the (-) ion is polyatomic, the end of the name changes to –ate or -ite. Carbonate (CO 3 2- )

4. Review: Compound- A pure substance made of 2 or more elements Ex) NaCl Ionic compound- A substance made of (+) and (-) ions Ex) NaCl Polyatomic ion- Ion made of more than 1 atom Ex) CO 3 2-