And we see that as we go across a period, our ionization energy of our atom tends to increase. And to explain that, let's look at Coulomb's Law. Now, Coulomb's law once again states that the force is equal to a constant k times charge q one times charge q two divided by the distance between them squared, where this guy is a charge due to the nucleus and q two is the charge due to the electrons. Now what happens as we move, for example, from lithium to fluorine? We already said that our effective nuclear charge tends to increase as we go from left to right. So fluorine has the highest force.