An atom that has either lost or gained an electron is called what?

An atom that has either lost or gained an electron is referred to as an ion. This occurs because the loss or gain of electrons alters the atom's electrical charge. When an atom loses one or more electrons, it becomes positively charged and is termed a cation. Conversely, when it gains electrons, it takes on a negative charge and is known as an anion.

Understanding this concept is vital because ions play critical roles in various chemical reactions and biological processes. For instance, they are integral in the formation of salts and conduct electricity in solutions. The distinction between ions and other terms, such as molecules or compounds, lies in their definitions: a molecule is formed when two or more atoms bond covalently, and a compound is made up of two or more different elements bonded together. Meanwhile, a neutron is a subatomic particle found in the nucleus of an atom, but it does not play a role in determining the charge of the atom. Therefore, the definition and characteristics of an ion precisely capture the phenomenon of an atom changing its charge through the gain or loss of electrons.