# Energy required to fully ionize Uranium

1. May 14, 2013

### doppeled

1. What is the maximum wavelength of light required to fully ionised Uranium to U92+, i.e.
strip it of all electrons and leaving a bare nucleus? For simplicity, only consider direct
ionisation and neglect non-linear effects.

Attempt at solution

Ok, so the electron structure of the atom is 2,8,18,32,21,9,2. Ionization will be the energy required to remove an electron that is the least tightly bound to the atom. In order to completely ionize the atom do I calculate the energy required to ionize each electron at their respective energy levels? I am a bit confused as to how to tackle the problem.
Thanks
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. May 15, 2013

### Staff: Mentor

I think this is where your confusion is coming from: these two statements of the problem are different.

You are not asked the total energy to ionize the atom, but the highest energy photon needed. Consider that one photon removes one electron, what electron will be the hardest to remove?

3. May 15, 2013

### doppeled

Ah yes, I think I understand now. So just a matter of calculating the energy required to remove an electron closest to the nucleus, which is in the ground state.

4. May 15, 2013

### Staff: Mentor

Just to make clear, it will be the energy needed to remove the last electron.

5. May 15, 2013

### doppeled

Yes so during ionization the outermost, least bound electrons will be removed first, and so by calculating wavelength required to remove the last electron we have a sufficient energy to completely ionize.