First, let's look at hydrogen, and then let's look at helium. Well, recall that hydrogen has exactly one proton and one neutron in its neutral state. And that means we can find the electrostatic force or the pull on this electron due to this proton by simply applying our coulombs equation. And this guy states that our force due to this electron or on this electron due to this proton is given by k, a constant times the charge of our proton, times the charge of our electron divided by our distance r between them squared. And this is the force that this guy feels due to this guy and also the force that this proton feels due to this electron. Now, note that their forces are negative, but they have the same magnitude.