In an atom, the number of electrons, which carry negative charges, is equal to the number of protons, which carry positive charges. This means that the total charge of an atom is balanced, and the atom is electrically neutral.

The number of protons in an atom determines its atomic number and also the number of electrons in a neutral atom. For example, carbon has an atomic number of 6, which means it has 6 protons and 6 electrons. This makes carbon a neutral atom, with a total charge of 0.

If an atom gains or loses electrons, it becomes an ion. An ion has a net positive or negative charge. For example, if carbon loses one electron, it becomes a carbon cation, with a charge of +1. If carbon gains one electron, it becomes a carbon anion, with a charge of -1.