Two-dimensional representations:

electron dot structures: pairs of electrons/single covalent bond represented by ··
e.g., H : H

structural formulas: single covalent bond represented by –
e.g., H – H
Covalent molecules have single, double and triple bonds.
Atoms can have a chainlike or ringlike structure, or branched chanins.
Molecular formula may represent more than one compound because atoms may form more than
one structure.
Structural isomers: substances with same chemical formula but different structure (does not include
rotations of bond electrons).