What is ionization energy?
A general term for the energy required to remove an electron from an orbital in an atom. Think of it also as the energy required to make a cation. Ionization energies are usually reported as the first ionization energy, second ionization energy, etc., with each subsequent ionization requiring more energy than the one before. How does the ionization energy relate to the valence electron number? The amount of energy required to remove an electron depends on if the electron removal (i.e. ionization) will bring the atom closer to or further from its nearest noble gas configuration. So, Na – and all the other group 1A elements for that matter – are one electron away from their noble gas configurations. As mentioned above, Na actually wants to lose that lone electron, so the first ionization energy is low. What about Na’s second ionization energy or Na’s first ionization energy? Intuitively, because Na is at the noble gas configuration, the ionization energy would be extremely high. In the e
