A fundamental property of matter. Protons and the nuclei of atoms have a positive charge; electrons have a negative charge; neutrons have no charge. Normally, each atom has as many protons as it has electrons and thus has no net electrical charge; in other words, it is neutral. Charged substances have an imbalance of positive and negative charges, a net charge that exerts a force on other charged substances. Charges that are both positive or both negative repel each other; charges that are different attract.