Additive Nature of Charge

Electric charge is ADDITIVE, exactly like mass: the total charge carried by an object is simply the algebraic sum of all the individual charges distributed across its different parts. The word 'algebraic' matters here -- when adding up the charges, their SIGNS (positive or negative) must always be taken into account, not just their magnitudes. So if two bodies carry equal but opposite charges, the net charge of the combined two-body system is exactly zero -- precisely the situation inside a neutral atom, where the nucleus's total positive charge exactly cancels the surrounding electrons' total negative charge, leaving the atom as a whole electrically neutral. …