Question

What is the difference between an atom and molecule?

Answer 1

The atom is the basic unit of matter while a molecule is a group of two or more atoms.

Answer 2

Atom is the basic element that constitutes various molecules, there are many atoms and each one has its own physical and chemical properties, they can occure in different ways in nature or might be very rare, molecules are atoms of same or different elements bonded together, there are few types of bondes that happenes between atoms of same or different elements to form molecule, these types of bonding and the geometry of molecule define the characteristics of molecule, i.e. its chemical and physical properties, you can find more on atoms and molecules in various elementary chemistry text books, or you can simply search google