3. Formulae

3.1. Molecular Formula and Structural Formula

Molecular formula
o Shows the actual number of each type of atom in a compound
o Does not show the way the atoms are joined together

Structural formula
o Shows the arrangement of atoms within the molecule
o It shows the sequence in which the atoms are bonded to each other

 
Butane

2-Methylpropane
Molecular formula  C4H10 C4H10
Structural formula  CH3CH2CH2CH3 CH(CH3)3

 
Ethanol
Molecular formula C2H6O
Structural formula CH3CH2OH not C2H5OH