ADEQ Water Distribution Grade 1 Certification Practice Exam

An ion is a charged particle formed when atoms gain or lose electrons. The essential idea is that a balance between protons and electrons is disrupted, giving the particle a positive or negative charge. In basic terms, this charged species is typically a single atom that has either lost or gained electrons, making it a monoatomic ion—like a sodium atom that has lost an electron to become Na+ or a chlorine atom that has gained an electron to become Cl-. While there are polyatomic ions that are charged molecules, the everyday definition centers on a charged particle arising from an atom, which is why this option best fits the general concept. The other terms describe what substances are or how they’re bonded (a molecule is two or more atoms bonded, an element is a pure type of atom, a compound is two or more elements bonded), but they don’t define the charged state that defines an ion.