Electrically charged particles are called ions. Ions can be either atoms or molecules, and they can have either a positive or a negative charge. The charge of an ion depends on the difference between the number of electrons and the number of protons.
If an ion possesses more electrons than protons, the ion has a negative charge. If the ion has more protons than electrons, then the ion has a positive charge. The numerical value of the charge is equal to the difference between the number of protons and the number of electrons. For instance, an atom with 20 protons and 22 electrons has a charge of negative two, while an atom with 15 protons and 12 electrons has a charge of positive three.