1. Counting Atoms

2. Vocabulary Elements: Cannot be broken down into smaller parts (off the periodic table) Molecule: Made of two or more atoms that are held together by chemical bonds Compounds: Consist of two or more elements bonded together. Coefficient: The big number in front of a Chemical formula that tells you the number of molecules Subscript: The small number that tells you the amount of each element

3. Examples: Element, Molecule, or Compound???? Fe Element…just straight off the periodic table Fe 2 Molecule…notice that it is more than one Fe Fe 2 O 3 Compound….more than one element

4. Steps to Counting Atoms First, write down each element in the compound. Ex: 3Fe 2 O 3 Fe and O Second, write down how much you have of each using the subscripts Ex: Fe=2 and O=3 Third, add up the total number. Ex: 2+3 = 5 atoms

5. Steps Continued Fourth, if there is a coefficient, multiply your total by the coefficient. Ex: 5 (total) x 3 (coefficient) = 15 atoms! THE END