The wave function of an electron of a hydrogen atom in the
ground state takes the form (r) = A e-r/ri, where A is a certain
constant, r1 i s the first Bohr radius. Find:
(a) the most probable distance between the electron and the
nucleus;
(b) the mean value of modulus of the Coulomb force acting on the
electron;
(c) the mean value of the potential energy of the electron in the
field of the nucleus.