What is an atom primarily defined as?

An atom is primarily defined as the smallest unit of a chemical element. This definition emphasizes that atoms are the fundamental building blocks of matter and can exist independently. Every chemical element is composed of atoms unique to that element, characterized by their specific number of protons, neutrons, and electrons.

In the context of chemistry, understanding that atoms serve as the basic unit helps explain how they combine to form molecules and compounds. Each atom retains the properties of the element it represents, allowing chemists to predict how different substances will react during chemical reactions. This clear distinction is crucial for comprehending concepts in atomic theory, molecular structures, and chemical interactions.