1. CH 7 Chem Formulas and Chem Compounds 7.1 Chemical Names and Formulas Formulas tell the kinds and numbers of atoms Molecular compounds: chemical formula tells number of atoms of each element contained in a compound Ionic compounds: lattice of positive and negative ions held together by mutual attraction

2. Monatomic ions – Cations: + charge (groups 1- 3A or 1-2,13); lose e- – Anions: - charge (groups 5-7A or 15-17); gain e- Naming monatomic ions – Cations: element name plus cation – Anions: element name with – ide ending plus anion

3. Common Monatomic Ions

4. Binary ionic compound: – Compound made of 2 elements – Use subscripts to have neutral compounds Nomenclature: – Naming system – Cation then anion

5. Polyatomic ions – Oxyanions: anion with oxygen

6. Naming binary molecular compounds – Uses prefixes – Order of nonmetals: C, P, N, H, S, I, Br, Cl, O, F

7. Naming Acids Acid; pH 0-6; higher concentration of H+ – 1: If anion ends in –ide, acid names begins with hydro- and has suffix –ic, followed by acid – 2:If anion name ends in –ite, acid name is stem with suffix –ous, followed by acid – 3:If anion ends in in –ate, acid name is stem with suffix –ic, followed by acid. – Use rules in reverse to write formulas!

8. 7.2 Oxidation Numbers

9. Nonmetals have multiple oxidation numbers Oxidation numbers are not charges! Oxidation numbers are like ‘bookkeeping’ to track overall e- distribution.

10. 7.3 Using Chemical Formulas Formula mass (molecule, formula unit, or ion) is sum of avg atomic masses of all atoms represented in formula Molar mass is numerically equal to its formula mass

11. Remember conversion factors Percentage composition: percentage by mass of each element in the compound

13. 7.4 Determining Chemical Formulas Empirical formulas: symbols with subscripts for whole number ratios of atoms in compound – Turn % into grams (out of 100g)

14. Empirical is smallest possible whole number ratio Molecular formula is actual formula for compound Use empirical to find molecular