In terms of ionization energy, the periodic trend is ionization energy will increase as we're moving from left to right across a period and up a group. So as we're heading towards the upper right corner of the periodic table, ionization energy goes up.
Here, if we take a look, we can see that the one with the lowest ionization energy is francium, which makes the most sense 'cause it's on the exact opposite pattern of the periodic trend. And we can see here that the one with the highest is helium. It's to the most top right corner of the periodic table.
Now, of course, there's going to be a little bit of some exceptions to this trend. We'll go into further detail about them. You'll notice here that nitrogen has a lower a higher ionization energy than oxygen. And you also notice here that beryllium has a higher ionization energy than boron.
There are other little subtle exceptions, but these four elements are the most commonly discussed when it comes to exceptions in ionization energy. So just realize that overall, as we head to the top right corner of the periodic table, ionization energy goes up.