Shown in the figure below is a "classical model" (i.e. before we knew about quantum mechanics) of an atom. Here an electron (m = 9.109e-31 kg, q = -1.602e-19 Coulombs) is orbiting a nucleus in uniform circular motion. The nucleus has charge Q = 1.7622e-18 Coulombs and the radius of the electron orbit is a = 1.58e-10 meters.