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