What is the term for an atom that has gained or lost electrons?

The correct answer is the term "Ion," which is defined as an atom that has either gained or lost electrons. When an atom gains electrons, it becomes negatively charged and is referred to as an anion. Conversely, when it loses electrons, it becomes positively charged and is called a cation. This change in the number of electrons compared to protons results in an overall charge, distinguishing ions from neutral atoms.

In contrast, a molecule refers to a group of two or more atoms bonded together, while a compound is a type of molecule that consists of two or more different elements chemically combined. An isotope is a variation of an element that has the same number of protons but a different number of neutrons. Understanding these definitions helps clarify the specific role that ions play in various chemical reactions and interactions in the field of chemistry, including its relevance to biological systems and processes.