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

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Counting Atoms!

Unit 3: Chemistry. Counting Atoms and Balancing Equations.Elements e.g.H2, Pb, C, K

Compounds e.g. NaCl, KOH, H2O2Chemical VocabularyUnit 3: Chemistry. Counting Atoms and Balancing Equations.Chemical Vocabulary

Subscripts: Indicates how many atoms of a particular element are present

Coefficients: Indicates the total number ofcompounds/molecules presentUnit 3: Chemistry. Counting Atoms and Balancing Equations.Counting Atoms1) List the different elements in each compound2) Count how many of that particular atom there are.3) Total how many atoms there are in the compound.

e.g. H2O

H (Hydrogen) 2 atomsO (Oxygen) 1 atom Total: 3 atomsUnit 3: Chemistry. Counting Atoms and Balancing Equations.More Examples3 H2O2 (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(NO3)2 Unit 3: Chemistry. Counting Atoms and Balancing Equations.How many atoms are in these compounds?KNO3

8 Cl2O

6 Ba(MnO4)2

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

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

Unit 3: Chemistry. Counting Atoms and Balancing Equations.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 EquationsAtoms cannot be created or destroyed by ordinary chemical means

Reactants ALWAYS = ProductsUnit 3: Chemistry. Counting Atoms and Balancing Equations.Law of Conservation of MassBalancing Chemical Equationshttp://www.wikihow.com/Balance-Chemical-Equations

Unit 3: Chemistry. Counting Atoms and Balancing Equations.You can ONLY modify the coefficient #

Balance H2 and O2 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. _H2 + _N2 _NH3 H: 2 H : 3 (Unbalanced) H: 6 H : 6 (Balanced) - New Equation 3H2 + _N2 2 NH3

Always double check your work by doing a final atoms count

Unit 3: Chemistry. Counting Atoms and Balancing Equations.Tips when Balancing