【sol】
Whether in Cartesian (x, y, z) or spherical coordinates, three quantities are needed to describe the
variation of the wave function throughout space. The three quantum numbers needed to describe
an atomic electron correspond to the variation in the radial direction, the variation in the azimutha
direction (the variation along the circumference of the classical orbit), and the variation with the
polar direction (variation along the direction from the classical axis of rotation).
1. Why is it natural that three quantum numbers are needed to describe an atomic electron
(apart from electron spin)?