2. Atoms and the Periodic Table
Periodic Trend: Atomic Radius (Simplified)
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As I stated before, as I move from left to right across a period, and as we move up a group, our atomic radius will decrease. Here I've reimagined the periodic table to show how the atomic radius changes as I move across it. Here we have hydrogen and its average atomic radius is 37 picometers, and we can see as we go from hydrogen to helium, the number drops. If we go to row 2, we have lithium, which is a 152 picometers, and as we go from left to right, we can also see for the most part the atomic radius will decrease. Now, of course, with chemistry, there are exceptions. A lot of these exceptions happen with the transition metal. We're gonna say the array the electron arrangement for transition metals makes their patterns less predictable, so we just don't include them. Now you don't have to memorize these numbers at all for each of the elements. All you need to remember is the general trend, and the general trend is as we head towards the top right corner of the periodic table, we expect the atomic radius overall to decrease. So just keep that in mind when you're looking at atomic radius.
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