The charge on an ion, declared by its number of electrons. A Cl- ion is in fact a Cl atom which has acquired an electron, and a Ca++ ion is a Ca atom, which has lost two electrons. Electrical charges work by moving from higher points to ones with less potential. The charges flow through negatively charged elections in external circuits after per the directions of pre-defined classical currents. For this reason, positive currents are made to flow in the opposite directions of the electron flow.