Chemical Symbols Law of Conservation of Mass l

Chemical Symbols

Law of Conservation of Mass l Matter cannot be created or destroyed. l Application: If a reaction starts with 5 atoms of nitrogen, those 5 nitrogen atoms must still exist at the end of the reaction. l If a reaction ends with 7 atoms of oxygen, the reaction started with 7 atoms of oxygen. l

Chemical Equations Describe the breaking and formation of chemical bonds. l The number of each atom must be the same on both sides of the equation because matter cannot be created or destroyed. l

Parts of a Chemical Equation l Reactants: The elements or compounds that enter a chemical reaction. l Found on the left side of the reaction arrow. 2 H 2 + O 2 H 2 O 2 Na + Cl 2 2 Na. Cl

Parts of a Chemical Reaction l Products: The elements or compounds produced by a chemical reaction. l Found on the right side of the reaction arrow 2 H 2 + O 2 H 2 O 2 Na + Cl 2 2 Na. Cl

Atomic Symbols Every element is found on the periodic table. l Each element has a 1 or 2 letter symbol. l l Oxygen =O l Tin = Sn l Sodium = Na l One capital letter per element

Chemical Formula Represent chemical substances with one or more element. l The subscript behind the element tells the number of atoms of that element. l l H 2 = 2 hydrogen l C 5 = 5 carbons l Sb 6 = 6 antimony

l Chemical Formula (con’t) If there is no subscript, there is one atom of that element. l Li l = one lithium The subscript only goes with the element behind it. l C 3 H 8 = Three carbon, eight hydrogen l P 5 O 3 = 5 phosphorous, 3 oxygen l Au. O = one gold, one oxygen

Chemical Formula (con’t) l The numbers in front of a chemical formula are called coefficients. l 2 Be l 3 N l 5 Bi

Chemical Formula (con’t) l To find the number of atoms, multiply the coefficient and the subscript l 5 C 2 = 10 carbon atoms l 3 Cl 2 = 6 chorine atoms l 7 As 5 = 35 arsenic atoms

Chemical Formulas (con’t) l The coefficient applies to all the atoms in a compound. l 2 H 2 O = 4 hydrogen atoms & 2 oxygen atoms l 3 CO 2 = 3 carbon atoms & 6 oxygen atoms l 5 Sn 2 S 3 = 10 tin atoms & 15 sulfur atoms.