Periodic Trend: Ionic Radius

by Jules Bruno
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for a majority. The periodic trends looking at the periodic table can tell you if they're increasing or decreasing in all our periodic trends were heading towards the top right corner and heading in that direction either increase or decrease that particular periodic trend. Now Ionic Radius doesn't fit into this idea. Ionic Radius does not involve looking at the periodic table. Or let's say Ionic Radius equals the distance between ions, nucleus and its outer shell. And the periodic trend is this. The Ionic Radius increases as the number of electrons of that ion increases. So we're going to say here, when we're looking at Ionic Radius, we're looking at ions and ions. CA need to be positive or negative for positive ions, which are cat ions were going to say cat ions tend to be smaller than their neutral parent form. So what do I mean by this? Well, if we take a look here at lithium, the lithium Adam is one s two to s one. It has one electron in its Valence electron shell. Right, because its second show only has one. When I become lithium ion, I lose one electron. I lose it from that Valence shell. So now the lithium ion no longer has two shells. It only has one shell that contains electrons, and we can see that there is a drop in the size for that particular ion. So just remember, the neutral form of the element is bigger than the cat ion form. So the general trend is losing an electron or electrons causes a decrease in your ionic radius. Now for looking at the and ions and ions tend to be larger than their neutral parent forms. Oxygen is one s two to s to to p four. Here these electrons air in the second shell and there's six of them total. When we become the oxide ion, we gain tomb or electrons. So now my outer shell has eight electrons. It may not be as a parent, but the anti on is slightly bigger than the neutral form. Because why, we said earlier, the Ionic radius increases as the number of electrons increases. So basically, mawr electrons equal larger ionic radius. So we're gonna say gaining an electron or electrons causes an increase in your ionic radius. So just remember, we don't look at the periodic table to determine the trend in Ionic Radius. Instead, we look at the total number of electrons that ion has the mawr electrons. It has the bigger its Ionic radius.