1. Writing Formulas and Naming Compounds Chapter 20 Section 3

2. Binary Compound Composed of two elements

3. Oxidation number How many electrons an atom has gained, lost, or shared to become stable Used to write Formulas – Least common multiple – Must have the correct number of positive and negative ions so the charges will balance

4. Naming Binary Ionic Bonds First element is the Cation (positive ion) – written as the name of the element Second element is the Anion (negative ion) – written with the root name of the element and the suffix –ide Ex. Sodium Chloride, Lithium Iodide, etc.

5. Polyatomic Ion Positively or negatively charged, covalently bonded group of atoms – Contains 3 or more elements

6. Naming A Polyatomic Ionic Bond Write the name of the Cation first then the name of the Anion To write the formula  use the oxidation numbers, their least common multiple, and put parentheses around the polyatomic ion before adding a subscript Ex. Ammonium Hydroxide – NH 4 OH Ammonium Carbonate – (NH 4 ) 2 CO 3

7. Naming Covalent Bonds Covalent bonds form from sharing electrons Written by using prefixes indicating how many atoms of each element are in the compound Ex. N2O5 – Dinitrogen pentoxide Number of Atoms Prefix 1mono- 2di- 3tri- 4tetra- 5penta- 6hexa- 7hepta- 8octa-