Western Governors University (WGU) SCIE1020 C165 Integrated Physical Sciences Practice Exam

The smallest unit that retains the properties of an element is the atom. An atom is composed of a nucleus, containing protons and neutrons, surrounded by electrons. Each element on the periodic table is defined by the number of protons in its nucleus, known as the atomic number. This fundamental characteristic gives the element its unique chemical properties.

In contrast, a molecule is made up of two or more atoms bonded together, which means it can represent a compound or a diatomic element, but it does not embody the essence of a single element. A compound, on the other hand, consists of two or more different types of atoms chemically bonded, and thus cannot represent a single element. An ion is an atom or molecule that has gained or lost one or more electrons, resulting in a net charge. While ions are derived from atoms, they do not represent the unaltered properties of the original element if they have changed charge. Therefore, the atomic structure is the basic unit that embodies the inherent characteristics of elements.