What is an atom called when it has a positive or negative charge?

An atom that has a positive or negative charge is referred to as an ion. This charge occurs when an atom either gains or loses one or more electrons. If it loses electrons, it becomes a positively charged ion, known as a cation. Conversely, if it gains electrons, it becomes a negatively charged ion, known as an anion. The defining characteristic of ions is their charge, which distinguishes them from neutral atoms.

In contrast, a molecule is formed when two or more atoms bond together, while an isotope refers to variants of an element that have the same number of protons but different numbers of neutrons in their nuclei. Lastly, the term "atom" simply describes the basic unit of a chemical element that comprises protons, neutrons, and electrons and does not inherently indicate any charge. Therefore, the term that correctly describes a charged atom is ion.