1. (2.2) CHEMICAL COMPOUNDS (p122-123; 126-127)

2. Chemical Formulas The short form of a chemical compound is called the chemical formula. H2OH2O Symbol for the element hydrogen. Symbol for the element oxygen. The small number (subscript) here means 2 atoms of hydrogen. No small number here means 1 atom of oxygen.

3. Compounds- 2 Types Compounds are formed when 2 or more elements combine. There are two main types of compounds: IONIC and MOLECULAR NaCl, K 2 SO 4 H 2 O, C 6 H 12 O 6

4. Ionic Compounds Ionic compounds are formed by combining a metal and a non-metal. The metal transfers electrons to the non-metal.

5. Ionic Compounds The positive (Na + ) and negative (Cl - ) ions are electrostatically attracted to each other. The bond formed by transferring electrons is called an ionic bond.

6. Characteristics of Ionic Compounds Brittle, hard, solids that can be crushed. Form crystals with well defined edges. Have very high melting points. Dissolve in water to release ions  conduct electricity.

7. Molecular Compounds Molecular compounds are formed by combining two non-metals. They do so by sharing electrons. The bond formed by sharing electrons is called a covalent bond.

8. Properties of Molecular Compounds Often soft, liquid, solid or gas. If they dissolve in water, they form solutions that do no conduct electricity. Tend to have relatively low melting points.

9. WORK Classwork Pg. 125 “Learning Check” #1-3 Pg. 123 “Learning Check” #1-4 Homework Ionic or Molecular? Interpreting Chemical Formulas