What is the smallest particle of an element that retains the properties of that element?

The atom is the smallest unit of an element that still retains the chemical properties of that element. An atom consists of a nucleus containing protons and neutrons, surrounded by electrons. While atoms can combine to form molecules and compounds, it is the individual atom that defines the element. For example, a gold atom is what makes gold gold. If you were to break down a gold atom further, it would no longer be gold. Molecules are formed by the chemical bonding of two or more atoms, and compounds are formed when atoms of two or more different elements chemically combine. Ions are atoms or molecules that have gained or lost electrons, acquiring an electrical charge.