What is the smallest unit of an element called?

The smallest unit of an element is called an atom. An atom is the fundamental building block of all matter and retains the chemical properties of that element. Each atom consists of a nucleus, which contains protons and neutrons, surrounded by electrons that occupy a defined space around the nucleus. This structure allows atoms to interact and form molecules, but on their own, they represent the simplest form of an element.

Molecules, on the other hand, are formed when two or more atoms bond together chemically. Ions are atoms or molecules that have gained or lost one or more electrons, resulting in a charge, while the nucleus refers specifically to the center of an atom that houses its protons and neutrons, rather than being a standalone unit of an element. Therefore, identifying an atom as the smallest unit captures the essence of what defines an element in chemistry.