Chemistry is the central science that studies matter and its transformations. It connects physics through atomic behavior, biology through life processes, and geology through Earth materials. Matter exists in three main states: solids with fixed shapes, liquids that flow freely, and gases that fill their containers. Understanding these fundamental concepts helps us explore how atoms and molecules interact to form the world around us.
Atoms are the fundamental building blocks of all matter. Each atom consists of three main components: protons with positive charge, neutrons with no charge, and electrons with negative charge. The atomic number, which determines the element's identity, equals the number of protons. For example, hydrogen has one proton, carbon has six protons, and oxygen has eight protons. Isotopes are atoms with the same number of protons but different numbers of neutrons, while ions have different numbers of electrons than protons.