Why does ionization energy increase regularly across the periodic table from group 1A to group 8A, whereas electron affinity increases irregularly from group 1A to group 7A and then falls dramatically for group 8A?

Video transcript

Hey everyone, we're told that ionization energy increases steadily from Group one A two group ate A across the periodic table. Yet electron affinity rises irregularly from Group one A two, Group seven A. Before sharply declining for group eight A. Why is this the case first? Let's go ahead and define ionization energy as we've learned, Ionization energy is the amount of energy required to remove an electron from a mole of gas phase atoms. So our ionization energy increases steadily when electrons are being taken out of the same shell and our effective nuclear charge is rising. Now let's go ahead and connect this with our electron affinity. So for electron affinity, this is the amount of energy released what an electron is added to a neutral atom to produce a negatively charged ion. So for electron affinity, addition of electrons move up a shell causing that uneven increase. So looking at our answer choices, it looks like answer choice C describes what we stated perfectly. So ionization energy increases steadily because electrons are removed from the same shell, whereas electron affinity rises irregularly because electrons are added to the next higher shell. And that's going to be our final answer. Now, I hope that made sense. And let us know if you have any questions