Ionization energies for helium

[Ripsirwin]

Homework Statement

The first ionization energy of an atom is the minimum energy needed to remove one electron. For helium, this is 24.6 eV. The second ionization energy is the additional energy required to remove a second electron.

a) Calculate the second ionization energy of helium.

b)What is the total binding energy of helium (the is, the energy to take it apart into two separated electrons and a nucleus

Homework Equations

none

The Attempt at a Solution

I figure that since the first ionization energy is 24.6 eV, the second will also be 24.6 eV. But it seems too simple to be right. doesn't the other electron play into the ionization energy of the first

 

[The_Duck]

It is easier to knock away the first electron, since it is being repelled by the other electron. The second electron is harder to knock away because it feels the full attraction of the nucleus. So you expect the second ionization energy to be larger than the first.

You need to find the binding energy of this second electron after the first has been knocked away. This is a hydrogen-like atom: look at how the binding energy of a hydrogen-like atom depends on the charge of the nucleus.