Theories of matter

Theories of matter describe how everything around us is made up of tiny particles. The classical view is that matter consists of atoms, which are indivisible units. Later, scientists discovered atoms are made of even smaller particles called protons, neutrons, and electrons. Quantum theory further explains that these particles behave both like particles and waves, and their exact locations are uncertain. Matter exists in various states—solid, liquid, gas—depending on how particles are arranged and how they move. These theories help us understand properties of materials and predict how they behave under different conditions.