1. The problem statement, all variables and given/known data It is known that the ionization temperature of hydrogen is T. Then, estimate the ionization temperature of the helium atom in terms of T. Assume that Bohr's theory is applicable, that is, All the electrons are occupying hydrogenic levels. By ionization temperature, we mean the temperature at which the atomic completely ionized(loses all its electrons). 2. Relevant equations Saha ionization equation 3. The attempt at a solution I am completely confused. When we are asked to assume that Bohr's theory is valid, then how do we account for the repulsion bw electrons in the same shell? Also, the Saha ionization eqn is valid for thermal equilibrium in which a fraction of atoms are unionized. Here we are dealing with a single atom.