An ion is an atom or a molecule that has a total number of electrons that is not equal to the total number or protons which gives the atom or molecule a net positive (electrons < protons, aka cations) or negative (electrons > protons, aka anions) electrical charge. Anions and cations can come together to form ionic bonds and neutralize the electrical charge, like in a molecule of salt (NaCl). When dissolved in water, the molecules of salt separate into their ions, Na+ and Cl-.

A radical is an atom or molecule that has an unpaired valence electron, but this atom or molecules does not typically carry a charge because the number of orbiting electrons still matches the number of protons in the nucleus, unless the atom or molecule also happens to be an ion. Radicals are very reactive and will form covalent bonds, which share electrons between atoms to complete an electron pair.

Ions have a charge, whereas radicals are neutral. Also, ions in nature tend to be compensated by ions with opposite charges, whereas radicals are very reactive and thus short lived.

An ion has a non-zero electric charge. A radical has an atom with unfilled electron shells and so is very reactive, but is electrically neutral.

An ion carries a charge, that means that the number of electrons and protons do not match. Electrons have a negative charge and protons have a positive charge. A radical has an unpaired electron, but does not have a net charge because the number of protons equals the number of electrons.