Question

what is an ion?
o an atom that has gained or lost electrons
o an atom with an unstable nucleus
o an atom with too many or too few neutrons
o an atom that emits radiation

Explanation:

An ion is formed when an atom gains or loses electrons, resulting in a charged particle. An atom with an unstable nucleus is a radioactive - atom. An atom with too many or too few neutrons may be an isotope or an unstable atom. An atom that emits radiation is also related to radioactivity.

Answer:

An atom that has gained or lost electrons