Organic chemists use a variety of ways to represent structural formulae of an organic compound.
Dot Structure (Lewis Structure)
This shows all the valence electrons. For example, given below is the dot structure of n-propyl alcohol.
Writing dot structure is tedious and time consuming. The other representations are more convenient and are therefore, more often used.
Dash Structural Formula
The pair of electrons forming the covalent bond is represented by a dash. A single dash represents a single bond, double dash is used for double bond and a triple dash represents a triple bond. The lone pair of electrons on hetero-atoms (like oxygen, nitrogen, sulphur, halogens, etc) may or may not be shown.