An atom is the smallest unit of ordinary matter that forms a chemical element. Every solid, liquid, gas, and plasma is composed of neutral or ionized atoms. They are incredibly small, typically around 100 picometers across. Atomic Structure Atoms are made of three main subatomic particles: Licensed by Google

: Negatively charged particles that orbit the nucleus in specific regions called shells or orbitals. They are much smaller than protons and neutrons. Key Characteristics

: Atoms can lose or gain electrons to become ions (charged particles) or vary their number of neutrons to become isotopes of the same element.

: This is the count of protons in the nucleus. For example, Hydrogen has 1 proton, while Gold has 79.