The force on either of the proton or the electron is given by k, a constant times q one, the q, or the charge of the protons times q two, the charge, the electrons divided by the distance between them squared. And what Coulomb's law does, it describes the force and electron experiences due to the pull of the proton nucleus. So let's look at two atoms, and let's compare these guys. 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.