Defining Atoms and Molecules
An atom is the smallest unit of a chemical element that retains the properties of that element. It is the fundamental building block of matter. A molecule is the smallest unit of a substance that can exist on its own and is formed when two or more atoms are chemically bonded together.
A Simple Analogy
Think of it like letters and words. An atom is like a single letter (e.g., 'H' for hydrogen or 'O' for oxygen). A molecule is like a word formed by combining those letters (e.g., 'H₂O' for water). The letters are the basic units, but they combine to form a new entity with different properties.