Fe iron Pb lead Au gold C carbon Co cobalt K potassium Ne neon N nitrogen

H2OH2O H is the symbol for Hydrogen O is the symbol for Oxygen The subscript means the molecule of water has two atoms of hydrogen No subscript after oxygen means the molecule of water has only one atom of oxygen.

Coefficient H2OH2O 3 Molecule of Water The coefficient shows the number of molecules of the compound.

+

C + O2O2 CO2CO2 REACTANTS are the starting materials on the left side of the arrow. PRODUCT is the new substance or substances produced and are on the right side of the arrow. yields or produces

NaOH + HClNaCl + H 2 O A plus sign separates products when there is more than one new substance produced. A plus sign (which mean combines or reacts with) separates the reactants.

Law of Conservation of Mass States that mass (atoms) cannot be created nor destroyed in a chemical reaction. There must be the same number of atoms on each side of the equation.

In a chemical reaction, the total mass of the materials formed is the same as the total mass of the starting materials.

10 atoms of O PP 4 O 10 O2O atoms of P 10 atoms of O = balanced

H + O 2  H 2 O H =1 atom O =2 atoms H =2 atoms O =1 atom = H + O 2  H 2 O2 O =2 atoms H =4 atoms 4 H =4 atom =

Mg + O 2  MgO Mg =O =

Ca + O 2  CaO Ca =O =

N 2 + H 2  NH 3 N = H =

Cu 2 O + C  Cu+ CO 2 Cu = O = C =

H 2 O 2  H 2 O + O 2 H =O =