In the early attempts to rationalize such spectra in terms of electronic motions one described an electron as moving about the atomic nuclei in circular orbits such as shown in Fig. 1. 3 Two circular orbits of radii ri and r2 Figure 1. 3. Characterization of small and large stable orbits for an electron movin around a nucleus A circular orbit was thought to be stable when the outward centrifugal force characterized by radius r and speed v(me vi/r)on the electron perfectly counterbalanced the inward attractive Coulomb force(Ze/r)exerted by the nucleus of charge v2/r=Ze/r 66 In the early attempts to rationalize such spectra in terms of electronic motions, one described an electron as moving about the atomic nuclei in circular orbits such as shown in Fig. 1. 3. Figure 1. 3. Characterization of small and large stable orbits for an electron moving around a nucleus. A circular orbit was thought to be stable when the outward centrifugal force characterized by radius r and speed v (me v2 /r) on the electron perfectly counterbalanced the inward attractive Coulomb force (Ze2 /r2 ) exerted by the nucleus of charge Z: me v2 /r = Ze2 /r2 r2 Two circular orbits of radii r1 and r2. r1