Ions are where atoms gain or lose electrons. If an atom loses and electron it becomes positive charge ( Cation) because there are more protons than electrons. The atoms' over all size also decreases as the remaining electrons are drawn closer to the nucleus. If an atom gains and electron it becomes a (Anion) and is negative charge because it contains more electrons than protons. The electron cloud also grows larger because there is more repulsion force than attraction force allowing the electrons to spread out.