The Language of Chemistry
Matter, Symbols, Formulas & Chemical Equations
Atoms
• All matter is composed of atoms. Atoms are often called the building blocks of matter
Element
• Matter that is made up of only one kind of atom
Is water an element?
Water contains two different elements: hydrogen and oxygen
NO
Compound• A substance composed of the atoms
of two or more elements joined together chemically
Examples of Compounds:• Water = H20
• Table Salt = NaCl
• Ammonia = NH3•
• Baking Soda = NaHCO3
• Chalk = CaCO3
• Octane = C8H18
Molecule
• A collection of atoms that move and act together as a single entity
• Atoms of a molecule are held together by chemical bonds
Atoms
H
Molecules
H2
Atoms
H O
Molecules
H2 H20
Atoms
H O N
Molecules
H2 H20 NH3
Chemical Symbols• Some symbols are a single letter as:
H, B, C, N, O, F, K
• Other symbols are 2 letters, but only the first letter is capitalized:
He, Li, Be, Ne, Na, Mg, Al
• Note: Co ≠ CO & Ni ≠ NI
Chemical equations tell you the following
• The substances that react together. • The substances that are formed. • The amounts of each substance
involved.• The arrow is read as "yields".
Chemical equations tell you the following
HCl + NaOH NaCl + H2O
ReactantsThe substances that
react together
ProductsThe substances that are formed
These numbers are found in a chemical equation
Subscripts The small numbers to the lower right of chemical symbols. Subscripts represent the number of atoms of each element in the molecule.
Coefficients The large numbers in front of chemical
formulas. Coefficients represent the number of molecules of the substance in the reaction.
These numbers are found in a chemical equation
Just as subscripts of 1 are never written, coefficients of 1 are not written either. Both are "understood".
2Fe2O3
coefficient subscripts
Using coefficients and subscripts to count atoms in equations:
• Multiply the coefficient in front of the chemical formula by the subscript after the atom.
# of atoms = coefficient x subscript
Example: How many atoms of hydrogen and oxygen are represented in 2H2O?
# of H atoms = coefficient 2 x subscript 2 = 4 # of O atoms = coefficient 2 x subscript 1 = 2
Using coefficients and subscripts to count atoms in equations cont:
• Atoms found inside parenthesis in a formula have two subscripts. The subscript to the right of the parenthesis goes to all atoms inside.
# of atoms = coefficient X subscript inside ( ) X subscript outside ( )
# of Al atoms = 2 X 2 = 4 # of S atoms = 2 X 1 X 3 = 6 # of O atoms = 2 X 4 X 3 = 24
Example:How many of each type of atom are represented by:
2Al2(SO4)3