Chapter 7, Problem 99AP

The formula for calculating the energies of an electron in a hydrogen-like ion is given in Problem 7.32, This equation can be applied only to one-electron atoms or ions. One way to modify it for more complex species is to replace $\text{Z with Z - }\sigma \text{or }{Z}_{\text{eff}\text{.}}.$ Calculate the value of $\text{σ}$ if the first ionization energy of helium is $\text{3}\text{.94 }\times {\text{ 10}}^{\text{-18}}\text{J}$ per atom. (Disregard the minus sign in the given equation in your calculation.)