Electrons and protons are the charged sub-atomic particles of atoms. Neutrons have no charge -- they are neutral. The magnitude of electrical charge is the same for both an electron and a proton, however, an electron is negatively charged, and a proton is positively charged. So, one electron and one proton exactly balance each other in terms of their electrical charge, so that they cancel each other out completely.

The charge on atom is determined by the difference between its number of electrons and protons. If there are more electrons than protons in a given atom, it will have a net negative charge. If there are more protons than electrons in a given atom, it will have a net positive charge. If the number of electrons is the same as the number of protons for a given atom, it will be neutral in its electrical charge.