So that means some atoms can pull away or can give off more than one electron. Now, the energy required to pull away that first electron is known as The First ionization energy, while the energy Required to pull away that second electron is Known as A second ionization energy and So on. Now let's look at the following now, the less likely an atom gives up the electron, the more energy is required to pull that electron off. 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.