The ion has fewer electrons.
Atoms vs. Ions. Atoms are neutral; they contain the same number of protons as electrons. By definition, an ion is an electrically charged particle produced by either removing electrons from a neutral atom to give a positive ion or adding electrons to a neutral atom to give a negative ion.
The answer is C.
An ion is unlike a neutral atom in the fact that it has a charge. Because electrons are negatively charged, an atom becomes more positive if electrons are lost.