The basic building blocks of matter are called atoms. Atoms are the smallest unit of an element and consist of protons, neutrons, and electrons. These particles combine in various ways to form molecules, which make up everything from the air we breathe to the food we eat. The arrangement and type of atoms determine the properties of matter, such as its state (solid, liquid, gas) and its reactivity. Each element on the periodic table corresponds to a specific type of atom, and understanding atoms is fundamental to the study of chemistry and physics.