In cesium atoms z 55 the 55th electron has principle

Question

In cesium atoms (Z = 55), the 55^th electron has principle quantum number n=6 and is outside closed shells, which partially shield the nuclear charge.

(a) First, suppose the shielding effect of the 54 inner electrons is perfect, and use the Bohr Theory to determine the ionization energy (in eV).

(b) If an "effective nuclear charge", Z_effe, experience by the outermost electron is to give agreement between Bohr theory and the measured Cs ionization energy of 3.98eV, what is Zeff?

(c) Use Bohr Theory, with this effective nuclear charge, to determine the average orbital radius of the outer electron.