When the proton number and electron number are unequal, the atom or molecule: ....
.... is an ion. < ----- this is the answer
An ion is a species (an atom of group of atoms) with excess of charge.
When the proton number exceeds the electron number there is excess of positive charge and the ion is positively charged. This kind of ions is named cation (positive ion).
When the electron number exceeds the proton number, there is excess of negative charge and the ion is negatively charged. This kind of ions is named anion (negative ion).
