1. Chemical Symbols and Formulas

2. Compounds are composed of more than one element. Their formulas have more than one type of symbol showing the different elements that compose that compound. Remember...

3. Constructed from the symbols of the elements composing the substances. EXAMPLE: NaCl is made of sodium (symbol = Na) and chlorine (symbol = Cl) Chemical Formulas Na Cl

4. A subscript is the little number that shows how many of each kind of atom are in the compound They are written to the lower right of the element symbol EXAMPLE: H 2 OHydrogen – How many? Oxygen – How many? When no subscript is written, it is a 1 Subscripts 2 1 O H H

5. The number that comes before the chemical formula and indicates the number of molecules present. EXAMPLE: 6H 2 O6 tells you there are six molecules of water Coefficients O H H O H H O H H O H H O H H O H H

6. CompoundFormulaCommon Name Sodium ChlorideNaClTable salt Dihydrogen MonoxideH2OH2OWater GlucoseC 6 H 12 O 6 Simple sugar Oxygen gasO2O2 Carbon dioxideCO 2 Carbon dioxide Nitrogen gasN2N2 Chemical Formulas you must know: