Atoms are the smallest unit of matter. Atoms are made of three subatomic particles- protons, neutrons, and electrons. Protons are positively charged, neutrons are neutrally charged (neither positive nor negative, or they have no charge), and electrons are negatively charged. In an atom that has no overall charge, the number of positively charged protons equals the number of negatively charged electrons. For example, a neutrally charged carbon atom has 6 positive protons and six negative electrons. Thus, its overall charge is:
6 + (-6) = 0
When the number of protons and electrons is not equal an atom will have an overall charge. This is called an ion. Cations are positively charged atoms. Cations have more protons than electrons. Anions are negatively charged ions. Anions have more electrons than protons.