1. Counting Atoms! Unit 3: Chemistry. Counting Atoms and Balancing Equations.

2. Elements e.g.H 2, Pb, C, K Compounds e.g. NaCl, KOH, H 2 O 2 Chemical Vocabulary Unit 3: Chemistry. Counting Atoms and Balancing Equations.

3. Chemical Vocabulary Subscripts: Indicates how many atoms of a particular element are present Coefficients: Indicates the total number of compounds/molecules present Unit 3: Chemistry. Counting Atoms and Balancing Equations.

4. Counting Atoms 1) List the different elements in each compound 2) Count how many of that particular atom there are. 3) Total how many atoms there are in the compound. e.g. H 2 O H (Hydrogen) 2 atoms O (Oxygen) 1 atom Total: 3 atoms Unit 3: Chemistry. Counting Atoms and Balancing Equations.

5. More Examples 3 H 2 O 2 (3 molecules of hydrogen peroxide) H (Hydrogen) (2 atoms x 3 molecules) O (Oxygen) (2 atom x 3 molecules) Total: 12 atoms Pb (Lead) 1 atom N (Nitrogen) (1 atom x 2 molecules) O (Oxygen) (3 atom x 2 molecules) Total: 9 atoms Pb(NO 3 ) 2 Unit 3: Chemistry. Counting Atoms and Balancing Equations.

6. How many atoms are in these compounds? KNO 3 8 Cl 2 O 6 Ba(MnO 4 ) 2 Unit 3: Chemistry. Counting Atoms and Balancing Equations. Counting Atoms

7. Unit 3: Chemistry. Counting Atoms and Balancing Equations. Balancing Chemical Equations

8. Chemical Equation Unit 3: Chemistry. Counting Atoms and Balancing Equations.

9. GOAL: There must be the same number of each atom on both sides of the equation. REACTANTS = PRODUCTS (LAW OF CONSERVATION OF MASS) Unit 3: Chemistry. Counting Atoms and Balancing Equations. Balancing Equations

10. Atoms cannot be created or destroyed by ordinary chemical means Reactants ALWAYS = Products Unit 3: Chemistry. Counting Atoms and Balancing Equations. Law of Conservation of Mass

11. Balancing Chemical Equations http://www.wikihow.com/Balance-Chemical- Equations Unit 3: Chemistry. Counting Atoms and Balancing Equations.

12. You can ONLY modify the coefficient # Balance H 2 and O 2 last If you have 3 hydrogen atoms on one side and 2 hydrogen atoms on another, try finding a common number between the two. E.g. _H 2 + _N 2  _NH 3 H: 2 H : 3 (Unbalanced) H: 6 H : 6 (Balanced) - New Equation 3H 2 + _N 2  2 NH 3 Always double check your work by doing a final atoms count Unit 3: Chemistry. Counting Atoms and Balancing Equations. Tips when Balancing