Formula for a compound indicates the elements that make up the compound and the number of atoms of each element present in the compound. The numbers of atoms are indicated by the u

e formula for a compound indicates the elements that make up the compound and the number of atoms of each element present in the compound.  The numbers of atoms are indicated by the use of small numbers called subscripts. 

Sometimes groups of atoms act as a single atom.  Such a group of atoms is called a polyatomic ion.  If a polyatomic ion is used in a formula more than once, it is put in parentheses and the subscript appears outside of the parentheses.  When a subscript appears outside the parentheses, it indicates that all the elements inside the parentheses should be multiplied by that subscript.  For example, the formula Fe(OH)3 indicates the combination of 1 atom of iron (Fe), 3 atoms of oxygen (O) and 3 atoms of hydrogen (H).

Name 

Use

Formula

Atoms in Formula

Calcium Carbonate

Limestone

CaCO3

Ca= calcium 1

C  = carbon 1

O = oxygen 3

Aspirin

Pain reliever

C9H8O4

Magnesium

Hydroxide

Found in milk of magnesia

Mg(OH)2

Paradichlorobenzene

Moth crystals

C6H4Cl2

Acetic acid

Found in vinegar

C2H4O2

Trinitrotoluene (TNT)

Explosive

C7H5(NO2)3

Calcium dihydrogen

Phosphate

Fertilizer

Ca(H2PO4)2

Name

Use

Formula

Atoms in formula

Pyrite

Fool’s gold

FeS2

Sucrose

Sugar

C12H22O11

Pentane

A component in gasoline

C5H12

Sulfuric Acid

Used in car batteries

H2SO4

Cellulose

Found in wood products like paper /pencil

C6H7O2(OH)3

Asbestos

Insulator

H4Mg3Si2O9

Dichlorodiphenyl-trichloroethane

(DDT)

Banned pesticide

C14H9Cl5

Silicon dioxide

Sand

SiO2

Iron oxide

Rust

Fe2O3

Butane

Lighter fluid

C4H10