NRCan X-Ray Fluorescence (XRF) Analyzer Operator Certification Level 1 Practice Exam

The idea is that a molecule is the smallest unit of a substance that still shows its chemical behavior when atoms bond together. A molecule forms when two or more atoms join in a specific arrangement, and this arrangement largely determines how the substance reacts and interacts with other substances. An atom represents the fundamental unit of an element, but the term in this context refers to a discrete unit that retains the chemical properties of the substance as a whole, which for compounds is the molecule. An ion is a charged form that may or may not be the substance’s basic unit, and an element is a pure substance made of one type of atom, not the smaller unit that embodies the compound’s properties. Therefore, the smallest unit that preserves the chemical properties of a substance is a molecule.