1. The problem statement, all variables and given/known data An unknown element has a nucleus with charge 14.00 e and a radius of about 3.60×10-15 m. How much voltage must be used to accelerate a proton (radius 1.20×10-15 m) so that is has sufficient energy to just penetrate the unknown element? Assume that the potential is that for point charges. 2. Relevant equations V = kQ/r 3. The attempt at a solution I tried calculating the two potential differences caused by the incoming proton and the positively charged atom, then adding them separately, but it seems that this isn't the right answer/ right approach. V = (8.99e9*(14*(1.6e-19))/3.6e-15) + (8.99e9(1.6e-19)/1.2e-15) = 6.79e6 V Any pointers would be very much appreciated!