Electronic Structure of the Atom; the Periodic Table

Atoms consist of a nucleus that is surrounded by a “cloud” of electrons. Protons, elementary particles carrying positive unit charge (e = 1.602 × 10–19 C), and neutrons, elementary particles carrying no charge, form together the nucleus of diameter of the order 10–14 m. Electrons, elementary particles carrying negative unit charge, have only about 1/1836 the mass of a proton, but are located within a relatively enormously large space of diameter of the order 10–10 m. Hence, with a view to mass distribution, the atom is largely “empty”.