okay guys what i want to do is i want to summarize this whole thing so we're looking at trends okay we're going to be looking at trends trends okay in the periodic table in the p p re or the oh my god handwriting is so bad in the periodic periodic table okay okay so what are the trends we're going to be looking at we're looking at atomic radius okay atomic radius that's not how you spell radius radius and ionic radius okay then we're going to be looking at metallic radius okay character then we're going to be looking at um electro negativity okay this is this is actually part of electro electro positivity okay and then the last one we're going to be looking at is ionization energy. So if I can't do this in one video, but we'll do it maybe in over two videos. So the first one is atomic radius and ionic radius.
Now, before we even go into this, I just want to remind you again, when we go down the periodic table, I want you to know that the number of protons is increasing, okay? So, which means that the Z, okay, Z is increasing. Now, what is Z again?
It's the nuclear charge. And what is nuclear charge? Nuclear charge is the attractive force of the nuclear charge. of the new of the proton side okay towards the electrons all right so protons are increasing okay so z is increasing but at the same time at the same time what is happening is the shielding effect is increasing much more okay why is the shielding effect increasing much more okay the first reason is distance Distance from nucleus is increasing. Second reason is there are more inner electron.
Shells, okay, there are more in electron shells. So as we go down the group, okay so basically what is happening is as we go down the group the As we go down the group what is happening is the effective nuclear charge the effective nuclear charge is getting is getting lesser so the as we go further away from go down the group right the valence electrons especially are slowly experiencing less and less and less attraction okay less less attraction. So like for example, in the case of let's say lithium, let's say sodium, potassium, rubidium, cesium, francium, right?
What is happening as you go down, the valence electrons of francium are held much more weakly. compared to incisium. The electrons in incisium are held more weekly compared to rubidium. And that's how it goes. And the same thing goes with other groups as well.
Okay. For metals, this is a good news because they love to lose electrons. Okay. They love to lose electrons. So the bigger they become, the more shielding they have, the avalanche electrons are held weekly.
Then the other thing I want to tell you is when we go across a period, okay, when we go across a period, what is happening is the The number of shells, number of shells remain the same, okay, remains the same. That means the number of shells are not changing. For example, let's say sodium, right? Sodium is 1s2, 2s2, 2p6, 3s1. And then if you look...
at silicon for example is 1s2 2s2 2p6 3s2 3p2 and then if you look at chlorine 1s2 2s2 2p6 3s2 3p5 so what i want you all to notice is this the number of inertials remain the same they are not changing Okay, any additional electron is just being added to the same outer shell. So so this is the valence shell for sodium This is the valence shell for Silicon. And this is the valence shell for chlorine.
So the inner shells are the same. But I wanted to also notice that the number of protons is increasing. So when we go this way, Z is increasing.
Okay, a nucleus charge. is increasing, but the shielding effect is more or less constant. It does increase a little bit, but we consider it more or less constant. So because of that, the effective nuclear charge, ZEFF, increases. increases that means the inward attraction force right the inward attraction force experienced by the valence electrons is increasing okay so in this case it's increasing much more so in the case of chlorine the inward attraction force is increasing much more okay so after explaining this and this so by now i hope you can understand if i told you when we're going down the group right the atomic radius is increasing okay atomic radius increases very easy because we are adding more and more electrons.
There are more and more shells. More electrons, more shells. Obviously, the size is going to get bigger, right? Also, if you want to use, you want to explain it in terms of shielding effect and nuclear charge. So, going down the group, nuclear charge is increasing.
But the shielding effect is increasing much more, okay? It's increasing much more. In fact, when you write answers in the exam, you don't even have to explain why.
It's increasing much more. And so, the effective nuclear charge experienced by the valence electrons is much. lower. That's why the size gets bigger.
And then when we go across, the atomic radius is getting smaller and smaller and smaller. And the reason is like what I just told you. The nuclear charge is increasing.
Shielding effect is constant. The effective nuclear charge experienced by the electrons, especially the valence electrons, is increasing. So all the electrons are being sucked closer to the nucleus. And so the atomic radius decreases. So with that, I have kind of explained.
explain this already to you okay atomic radius now in terms of ionic radius right when we talk about ionic radius we we have two groups we have two groups right one one we have metals okay we have metals and then the other one we have non-metals Now for metals, you see what happens is they lose their valence electrons. So like for example sodium right is 1s2, 2s2, 2p6, 3s1. But when it becomes sodium ion, obviously I hope you can see this.
It has lost its valence electron, right? Can you see this? So which means that now the size has become smaller. So in the case of positive ions, whenever you produce positive ions, they're always smaller than their atoms because they just lost a shell. When they lose a shell, obviously they're going to become smaller, isn't it?
So you can see like from here, this is the distance and then from here the distance is shorter. I mean, it's obvious. But when it comes to non-metals, what is happening is... We are adding electrons. Okay, we are adding electrons.
Let's say, for example, let's say we take phosphorus, right? Phosphorus is 1s2, 2s2, 2p6, 3s2, 3p3, right? What happens in the case of phosphorus is it becomes phosphide ion.
So now it has 15 protons and it has 18 electrons. Initially, it had 15 protons and 15 electrons. So not a problem. Number of protons and electrons are the same.
the same. But now as you add more electrons, what is happening is there are more electrons. So when there are more electrons being added, the repulsion between electrons increases because electrons are negatively charged. So the repulsion increases and when repulsion increases, what happens is the atomic volume has to increase.
That means like if this was phosphorus, to minimize the repulsion, that means the electrons are fighting with each other, right? To minimize the repulsion, the atomic radius has to increase. It has to become bigger so that the amount of repulsion decreases, okay?
So in the case of negative ions, they're always bigger. than their atoms, right? And the more electrons you add, the bigger they become, okay?
More electrons you add, the bigger they become. So that explains this part as well, okay? Ionic radius. So it does explain this.
Now, the other thing I want to explain to you is metallic character and electropositivity as well as electronegativity. Now, earlier I told you what is happening is when we're going down the group, right? We're down the group, the valence electrons are held weakly. easier to lose electron so easier to lose electron easier to lose valence electron right easier to lose valence electron it means electro electropositivity increases so electropositivity is the ability to lose electrons okay or ability to lose the valence electron so going down the group electropositivity electropositivity increases it becomes easier to lose electrons And when it becomes easier to lose electrons, you become more, more metallic.
Because metals love to lose electrons. So going down a group, metallic character increases because you're becoming more electropositive. But on the other hand, And when you go across, right, when you go across, what is happening is the ZEFF, or effective nuclear charge, is increasing.
So what is happening is when you go this way, it's harder to lose valence electrons. Okay, harder to lose valence electrons, which means that metallic character, decreases it becomes less metallic but if it's harder to lose electron it it basically means it is easier easier to gain electron it becomes easier to gain So which means that to gain electron, this character is called electronegativity. So which means that if electropositivity decreases, electronegativity, that means the ability to pull electron increases.
So electronegativity is the ability to full electrons okay so if electropositivity increases electronegativity decreases so like in this case here just now i told you going down electropositivity increases so which means that electronegativity will decrease and then in this case like say in this case just now if you're going this way okay if electro positivity decreases it means electronegativity that means ability to pull electrons increases okay so that explains this part on metallic character so going down metallic character increases going right left to right metallic character decreases so going up to down electropositivity increases the misability to lose electron increases but going from left to right electropositivity decreases harder to lose electrons harder to lose electrons basically means easier to pull electrons that means electronegativity is increasing then that leaves us with ionization energy. Okay, ionization energy. And I think for this one, I want to create a separate video to explain this to you.