What is the smallest unit of matter?

An atom is defined as the smallest unit of matter that retains the properties of an element. It is composed of protons, neutrons, and electrons, which are the fundamental building blocks of all matter. Atoms can combine to form molecules, which are groups of two or more atoms bonded together. However, individual atoms themselves cannot be broken down into smaller parts without losing their elemental properties. This distinction is important in understanding chemistry and the structure of matter.

While a molecule represents a combination of atoms, it is not the smallest unit, as it consists of multiple atoms bonded together. A particle may refer to any small unit of matter, but it does not specifically denote the foundational aspect of an element. A compound, on the other hand, is made up of two or more different types of atoms chemically bonded together, which also makes it larger than a single atom.