What is the smallest chemical unit of an element?

The smallest chemical unit of an element is an atom. An atom is the basic building block of matter and retains the properties of the element it represents. Each element on the periodic table is composed of atoms that contain protons, neutrons, and electrons. The structure and arrangement of these subatomic particles define the characteristics and reactivity of that particular element.

Molecules, while important chemical entities, are formed by the combination of two or more atoms bonded together. Therefore, they represent a grouping of atoms rather than the smallest unit of a single element. Ions are atoms that have gained or lost electrons, resulting in a charge; they are not the fundamental units of an element but rather modified forms of atoms. Similarly, cations are a specific type of ion that has lost electrons and carries a positive charge, making them further examples of derived units rather than the basic building block of an element. Thus, the atom stands as the essential unit when discussing the smallest chemical unit of an element.