2. A molecule is a group of 2 or more atoms linked together chemically. Ex: H 2 0, CH 4, O 2,H 2,O 3 A compound is a molecule that contains 2 or more different atoms. Ex: CH 3 COOH (vinegar)

3. Interesting molecules The caffeine molecule Lactic acid (in milk) Adrenalin!

4. Sugar C 12 H 22 O 11 Vitamin C Fat molecule

5. Are you hungry?

6. Properties of molecules A molecule has different properties than the atoms it’s composed of. Example: Sodium, Na, is a reactive metal and chlorine (Cl is a toxic gas!) But the two atoms linked together give table salt, that we eat. NaCl

7. Nomenclature and chemical formula Chemical formula: it is the name of a molecule using symbols. Ex: NaCl, H 2 O, l, etc. H2OH2O Subscript: indicates how many atoms are present. Affects the atom on the left of it. There are 2 atoms of H and 1 atom of O H 2 SO 4 has 2 atoms of Hydrogen, 1 atom of sulfur, and 4 atoms of oxygen.

8. Let’s practice! Tell how many atoms of each kind there are in the following molecules: a)MgCl 2 b)Al 2 O 3 c)H 3 PO 4 d)NH 3 e)HCN f)C 2 H 2

9. Nomenclature: is the scientific name we use to name a molecule. The common name of NaCl is table salt. The scientific name is sodium chloride. The common name of CH 3 COOH is vinegar! The scientific name is acetic acid.