(5-18)   ①  We have equation V-17 to allow us to calculation energy as a function of distance from the nucleus:

You can use this, together with your calculated value of <r> from Question 5-16, to estimate the ionisation energy (remember that ionisation means, in effect, removing the electron to infinite distance from the nucleus).

②  The number you calculate may not mean much to you – it looks like a small number but then it’s only for one atom and that’s an unfamiliar scale. How you deal with this depends on whether, at heart, you are a physicist or a chemist. Nefertiti is in the physics camp. If you’re with her, you’ll want the number in eV (electron volts), which is the units physicists generally use for the energies of interaction of individual particles on the subatomic scale. It’s an easy conversion:  1 eV = 1.602 x 10-19 J.

③   You may be more of a chemist, in which case you would like the number in their preferred unit, which is kJmol-1. Amadeo Avogadro is on hand to remind you that his number – the number of particles in 1 mole -  is 6.02 x 1023. And Josef Loschmidt is also on hand to remind you that Amadeo didn’t measure the number, he did. Cormorant observes that chemists can argue just as well as physicists.