Periodic Trend: Atomic Radius

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.

So remember we said the general trend is as we had from left to right and up a group are atomic radius will decrease. So remember, as we had up a group, we say that the number of shells is going to decrease, so this causes a decrease in my atomic radius at the same time as removing from left to right of the periodic table. We're going to say that the shell number stays constant, but the number of electrons within that shell is increasing. This causes greater attraction to the nucleus which compresses the atomic radius a bit. So if we take a look here, we can see that typically we have our atomic radius given to us within PICO meters. We can see that hydrogen is pretty small at 37 PICO meters and we can see that as we head from hydrogen to helium, there's a small decrease. Now off course, there's gonna be exceptions here and there. Ah, lot of them happen within the pit here with our transition. Metals also realized that the last world, the periodic table, those elements because they're so large and so heavy because they've been synthesized in laboratories. There a little bit unstable, so we don't have definitive information on terms of their atomic radius. So we just leave them out and realize that we have our other transition metals that are below this, our inner transition metals. They have the same issue. So when it comes to atomic radius, these are the ones that are most important. You're not expected to memorize these numbers, so don't worry. You just need to understand the general trend. And it is as we head towards the top right corner of the periodic table. Atomic Radius, for the most part, will decrease. So keep that in mind when looking at questions dealing with atomic radius.

So here it says which of the following Adams has the largest atomic radius. So here we're looking at K R. B. Why s r and CIA? So to make a little bit harder, I removed the values. Now you can go and take a look, but just rely on the general trend. We said as you had towards the top right corner, your atomic radio should decrease. But here we're looking for the largest atomic radius, so they could think of it in the opposite way. Who's the furthest from the top right corner? The answer would be RB R B would be the one here with the largest atomic radius based on. The choice is given to us. So just remember that general trend it would be larger than all of the others presented before us.