How is an atom defined in chemistry?

In chemistry, an atom is defined as the smallest unit of matter that retains the properties of an element. Atoms are the building blocks of everything around us, including all substances in the natural world. Each atom consists of a nucleus made of protons and neutrons, surrounded by a cloud of electrons. This fundamental role means that atoms can combine to form molecules and compounds, but they themselves cannot be broken down into smaller particles without losing their essential characteristics. By understanding that an atom is the smallest unit of matter, one can appreciate the complexity and diversity of matter derived from various arrangements and combinations of these atoms.