An atom is electrically neutral when it has an equal number of protons and electrons. Protons carry a positive charge, and electrons carry a negative charge of the same magnitude. Therefore, when their numbers are equal, the positive and negative charges cancel each other out, resulting in no net electrical charge for the atom. Neutrons in the atom have no charge and do not affect the electrical neutrality. If an atom gains or loses electrons, it becomes an ion and carries a net positive or negative charge, thus not being electrically neutral anymore.