Chemistry: Atomic Structure, Ions, and Isotopes Key Concepts

Ion

An atom or molecule with a net electric charge due to gaining or losing electrons

Cation

A positively charged ion formed when an atom loses electrons

Anion

A negatively charged ion formed when an atom gains electrons

Isotope

Atoms of the same element with the same number of protons but different numbers of neutrons

Radioisotope

An unstable isotope that emits radiation as it decays

Neutral Atom

An atom with equal numbers of protons and electrons and no charge

Polyatomic Ion

A group of bonded atoms with an overall electric charge

Monatomic Ion

An ion formed from a single atom that has gained or lost electrons

Allotrope

Different structural forms of the same element in the same physical state

Atomic Mass (Mass Number)

The total number of protons and neutrons in an atom's nucleus

Atomic Number

The number of protons in an atom's nucleus that defines the element

Elemental Form

An element in its pure form, not combined with other elements