Question

an atom that has either lost or gained neutrons. isotope atom ion quark

Explanation:

An isotope is defined as an atom that has either lost or gained neutrons. This change in the number of neutrons affects the atomic mass but not the atomic number (since protons remain the same). An atom is the basic unit of matter. An ion is an atom that has lost or gained electrons (resulting in a charge). A quark is a fundamental particle that makes up protons and neutrons.

Answer:

Isotope