What is an atom?

An atom is defined as the smallest unit of an element that retains its chemical and physical properties. This means that each atom is the fundamental building block of matter and exhibits the characteristics of the element it represents, such as reactivity, mass, and electronic structure. An atom consists of protons, neutrons, and electrons, and the arrangement of these subatomic particles determines the properties of the element, including its behavior in chemical reactions.

Understanding this definition is crucial because it distinguishes an atom from other chemical structures. For example, a compound is made up of two or more atoms that are chemically bonded, but it cannot apply to an individual atom. Similarly, while atoms can form molecules, referring to atoms as a grouping is misleading since it implies a larger structure rather than highlighting their fundamental nature. Lastly, atoms are not the largest units of chemical structure; instead, they are the smallest, as larger units such as compounds and mixtures are made up of multiple atoms.