An atom consists of three sub-atomic components; protons, neutrons and electrons. The nucleus contains protons and neutrons. Electrons orbit the nucleus. Protons have a positive charge, electrons have a negative charge and neutrons have no charge.An ion is a charged particle, containing more electrons than protons or vice versa. An atom can gain an electron to become a negatively charged ion (anion) or an atom can lose an electron to become positively charged (cation).