Ionic and Atomic Radius

[Diego Salgues 2K]

Anyone have a super concise and memorable way to memorize the trend of Ionic and Atomic radius across the Periodic Table?

[Clayton Dinh 3C]

The general rule is that atomic radius increases as we go down a group and decreases as we go across a period. I think the logic behind this is that energy levels increases as we go down a group which is a direct correlation with the radius of the atom. As we go right of a period, the increase in amount of electrons increases the attraction between the protons of the nucleus and the electrons in the orbitals, pulling the orbitals closer to the nucleus.

[Josh Richter 2C]

I think the best way to recall that atomic radius increases as you go down and to the left on the periodic table is to understand why it happens. As you go down each group, there is another shell, so the atomic radius will be bigger. As you go down each period on the periodic table, there are no more shells, but the attraction between the nucleus and electrons increases with more protons and electrons, so the atomic radius decreases. I know this might seem harder to understand at first than just memorizing the rules, but it definitely will make it more memorable later on in the class when you can actually deduce the rules for yourself instead of trying to to recall what you learned a couple of weeks ago.

[Josh Richter 2C]

For ionic radius, the same rules apply with atomic radius but we just treat them based on the atoms they are isoelectronic with. However, I think most of the problems with ionic radius have to do with ions that have the same number of electrons, in which case whichever ion that has the most protons will have the smallest atomic radius because there would be a stronger attraction between the nucleus and the electrons.

[Lizzy Bulla 3K]

As you go from left to right, the ionization energy increases which means that the atomic radius decreases as you go left to right.

As ionization energy increases, this means that it takes more energy for the electron to be removed which means the electrons are more tightly bound and the atomic radius is smaller.