So Atomic radius is the distance between Adams nucleus and its outer electron shell, otherwise known as its valence shell. So here, if we take a look, we have our nucleus in the middle. And here we have our outer shell. The distance between the nucleus and the outer shell is our atomic radius. R. Now remember, within the nucleus we have our protons and neutrons are protons are positively charged particles. Neutrons are neutral and the nucleus itself contains our proton and our neutron. Now we're gonna say, here, going down a group, we're going to say that the number of electrons increases because our shells get larger and larger and they can hold more and more electrons. And we're gonna say that the number of electron shells also increase. But we're going to say, moving across the period. Though we're going to say that the number of electrons with within the same shell also will increase. We're gonna say increasing the number of shell electrons in the same shell causes greater attraction with the nucleus. And what this does is it causes a slight decrease in our atomic radius. So we have these two forces at work. We're adding more electrons, and as a result our Adam gets larger and larger with more and more shelves. But as we add more and more shells, there's gonna be more electrons found within each of those shelves. This is going to cause some issues with our atomic radius, so there's an increase in a decrease type of phenomenon happening here with the increase of the number of electrons. The overall periodic trend is that as we move from left to right, so remember, we're always heading towards the top right corner of the periodic table. Are atomic radius will decrease? So click on to the next video and let's take a look at what this periodic table would look look like in terms of atomic radius.
