What is the difference between Lewis structure and bond line notation?
Lewis structures show every atom, bond, and lone pair of electrons. Bond line notation omits lone pairs, C atoms, and H atoms attached to C.
The Lewis structure is
The bond line notation for butan-1-ol is
The vertices and the end of the line represent the carbon atoms.
The end carbon atom (C-4) contains three H atoms, since it has formed one bond to C-3.
The other three carbon atoms each contain two H atoms, since they have formed bonds with two other atoms.