Bonding (Ionic, Covalent & Metallic) - GCSE Chemistry

Chemical

bonding

is kind of like Sudoku, you just need to remember a couple of rules and if you remember them you'll be fine, so let's take a look at our periodic table first of all, because this is really important. I have written here that the groups. one two jump in all the transition metals 2 3 4 5 6 7 8 and I put a 0 there and I'll talk about that in a second we have this ladder starting with aluminum which is a metal and goes down like this all the way to the one on the left which is a metal , everything on the right is a non-metal, this is the first thing you need to remember: metals bond to non-metals

ionic

ally, that is

ionic

bonding

.

I'll talk about what that means in a second bonding of the non-metals

covalent

ly, eventually the metals bond with each other. Read

metallic

, so there we go to three very important things that you need to remember now in this video you're going to hear me talk about atoms that want a full outer shell of electrons, so I'm going to anthropomorphize these atoms because that's how I roll, but you should never in a test it says that an atom wants to gain or get rid of electrons, but if it helps you understand things better like it did for me, here you go, we'll cover

metallic

bonding real quick because it's really easy. all you need to know about metallic bonds is that we have positive ions, a lattice of positive ions, a lattice of positive ions, it just means a grid and write positive as that lattice of positive ions surrounded by a sea of ​​delocalized electrons, delocalized only It means that they are not in the atoms themselves. and we know that has to be true because we said that we have a network of positive ions.

An ion is any atom or molecule that has lost electrons at GCSE. You may hear the term negative ion. Okay, not really true, but we'll stay. with this for now, but here we are talking about positive ions of proper ions and by the way, this is the reason why metals are good conductors because the electrons are delocalized, they can flow easily, so we can forget about the metallic links. Choose any metal, let's take iron, why? No, if you have a bunch of atoms that you put together, they will form this positive iron lattice with the sea of ​​delocalized electrons.

Okay, let's get to the good stuff. So let's talk about ionic bonding first because I think it's a little bit easier than

covalent

bonding. What you have to remember at all times is that all atoms want is a complete outer shell of electrons and that applies to both ionic bonding and covalent bonding, but they achieve it with different means now, the group that is the column in the periodic table of an element. tells you how many electrons Adam has in his outer shell and that's why if we take a look at group eight, helium, neon, argon, krypton, xenon and radon, these are what we call noble gases, because they are very, very, very unreactive, now you might be telling them that they don't react at all when, in fact, that's almost true, they basically don't react because they already have this whole outer shell of eight electrons and that's what most atoms want, that they don't They want more electrons.

They don't want to give anything away, they don't want to earn more, they are happy, they are noble, but for the rest of the rabble elements on the left, none of them have a complete outer shell of electrons, generally when we look. In the ionic bond we are observing the elements of group one and two, so we are talking about lithium, beryllium, sodium, magnesium, potassium and calcium. Those are usually the metals involved. How many electrons does lithium have in its outer shell? Well, he's in the group. one, then it has an electron in its outer shell.

I'll tell you what. I'm going to draw a lithium atom. There you have it. I have drawn only its outer layer. I don't need to draw the layer below. What about magnesium? in group two, that means it has two electrons in its outer shell again. I don't need to draw the inner shells which is a bit of a shortcut, now both lithium and magnesium want a full outer shell of electrons and that means eight electrons, how many? Lithium has to gain electrons. It has one, so it needs to gain seven electrons. Magnesium has to gain six.

That sounds like a lot of work. Is there anything easier you can do? Yes, instead of gaining electrons, what they can do is gain. getting rid of its outer electrons to leave its outer shell empty, so it's actually no longer its outer shell, it's the layer below that is not the outer shell. The same thing happens with magnesium and that's something you have to remember is that metals always donate the electrons that are given to them. electrons away it gives it to non metals now when lithium gives away this electron I can extract it like this and I'm just going to extract its electron flying like this okay it's gone somewhere else I don't really care it's gone now lithium, now lithium is missing an electron and because electrons are negative, if we have less, that means lithium becomes L I Also, now it is an ion because it is no longer neutral, it has a charge, what What happens to magnesium if it gets rid of its two outer shell electrons? we're just in negatives so we take away two negatives and we end up with two positives so mg becomes mg 2 plus each metal in group one forms ion one and we don't write the one we just write a plus each metal in group one two forms the two plus ion, so whenever these metals are bonded to a nonmetal, we have Li plus na+ k+ r b+, etc. be2 ​​plus mg 2 plus CA 2 plus and so on, that's how it always is, what about non-metals? metals except electrons, because they accept them from metals, right?

Let's have an example. Let's go with chlorine, so chlorine has seven electrons in its outer shell because it's in group seven again. You want a full outer shell of electrons, that's right. It's going to get rid of its seven electrons like metals, no, of course, no, it's much easier for it to accept an electron from one of these, say from lithium, and now it has a complete outer shell again, although it is no longer CL. neutral, we add an electron, we add a negative, it becomes CL. What happens if we have oxygen? Oxygen has six electrons in its outer shell.

How many want to have a full outer layer that's right on it? So, let's say. that gets the two electrons from magnesium and now has eight electrons in its outer shell, is happy so to speak, but of course it is no longer just oxygen, it is an ion, not quite, but let's say like an ion, but it is There are going to be two, because it has gained two electrons and negative electrons, so what could they ask you about this? Well, you might be asked to provide the chemical formula for a certain ionic compound now, when things bind to ionic Li, they don't actually form molecules.

What happens with ionic compounds is that we end up with a network similar to that of metallic bonds, but instead of just positive ions, we actually have just a grid of positive and negative ions, all together in a nice grid, there is no a single molecule, that's all. just a big crystal, a bigger lattice of these ions, okay, so let's say we're asked to find the chemical formula which is the symbolic form of a certain ionic compound. Let's go with lithium fluoride. Now lithium is in Group One, meaning it has one electron in its outer shell, what do you need to get a full outer shell?

Well, you just need to lose that electron. If you lose one electron then your ion is Li and as we just saw fluorine is in group seven meaning it has seven electrons in its outer shell so it needs to gain one electron to have a full outer shell , so what is its ion? These two now have a full outer shell. Where has the lithium electron gone? It's gone to the happy days of fluorine if we put these two together, do the pros and cons, the charges balance, yes, so we can say that actually the chemical formula of lithium fluoride is LI.

If we have the charges there, they are still there, but we don't have them. I need to write them down because they are all balanced, what about lithium oxide? So again, we know lithium ion is a lie, but what about oxygen? Well, it's in group six, so we know it needs to gain two electrons, huh? So if putting these two together we now have one more lie +o2 - then we have one positive charge and two negative charges that don't balance each other, so that doesn't work, what do we have to do instead if we double the number of Li lithium - oh, that means now that we have two advantages - - and therefore that solves the charges or balances, let's go for magnesium chloride.

Magnesium is in group two, so it has to form one more two ion. Chlorine is in group seven. Excuse my ELLs, that's how I write them, they almost look like YZ, but they're just curly. Chlorine is in group seven, so it only has to gain one electron to have a full outer shell, so once again my charges are not balanced. I have to increase magnesium and one less in chlorine, what do I have to do right? I have to double the bleach, so now I have two plus two; you could have gotten two and that works, so whenever you are asked to give the chemical formula for an ionic compound, you just need to double or triple things so that the positive and negative charges balance out.

Let's try a harder one: aluminum oxide. Now I'm going to put three aluminum oxides in there if you see a Roman Numeral after the metal that tells you what ion it produces, so it will produce well. We know it will be more because all the metal ions are positive, but it will be the three plus oxygen, as usual, there are two. Oh my gosh, these Definitely don't balance because we have a three plus in the aluminum two: in the oxygen, what do we need to do to make them balance? We need to multiply them so that we have the same graph if we do both.

We ended up with six more because we have two batches of this, so what do we have to do with the oxygen? We have to triple it six plus six; the works are good, so what about the dot and cross plots? So let's go with lithium. fluoride, all we have to do is draw our lithium and a fluorine, we're going to put brackets around it and we're going to put the electrons for fluorine one, two, three, four, five, six seven, and we know that it has gained a electron from lithium, so we give it that and cross over now that the electron has disappeared from lithium, so we're not actually going to draw that electron in this and draw what happened in the end with both atoms when they finally become ions.

All we have to do is put the sign for the positive ion and the negative sign for the fluoride ion. What about magnesium chloride? Well, similar idea we'll just draw the magnesium again. We know it's going to end up with an empty outer shell there and We're going to write two chlorine there, we're going to stick electrons that we know it gained an electron from magnesium. I mean chlorine is, and we know magnesium is, more, but the thing is, we know magnesium chloride is. mgcl2, so let's limit it down there to show that we do indeed have a lot of chloride ions/magnesium ion.

Now hydrogen is technically in Group One because it only has one electron in its outer shell and that kind of makes it a metal, but hydrogen is a little special because it can bond Li ionic and covalently. Actually, it's somewhere in between. What we're going to follow is that you can do both. An example of hydrogen bonding with ionic Li is hydrochloric acid, which is HCl. The ions that form this are H+ and Cl. Let's think about another acid and also the sulfuric acid h2so4. Now, what are the ions that make this up? Well, there's a lot of H+, so where do they both come from? to balance the two H plus, well, you may or may not know that so4 is its own iron and has to charge two;

This is an example of a molecular ion, let's think about the last common acid we have, so hno3 again h plus is always the ion. of hydrogen, that must mean that this molecular ion here is the non-3 nitrate ion. What happens to hydroxides? We have talked about acids, let's talk about alkalis. We know that sodium is in group one, so it always forms the na plus ion so that means this Oh H again is a molecular ion which we call a hydroxide ion and it has the charge, so it's an OH, and there are all kinds of different molecular ions, but those are the most common ones we deal with, so what happens? when non metals bond with each other we said it is a covalent bond now here is the problem let's say we have two fluorines that want to bond together they both have seven electrons in their outer shell and one of the fluorines will give one of their electrons the other one is fine, well one of the fluorines ends up with a complete outer shell, but then the other one only has six electrons, that's no use, what do they do instead of donating and accepting electrons, they share electrons and again that is to get a complete outer shell, so let's take fluorine, here we call group seven elements halogens and all of these spin in pairs and that's because they can't spin on their own because they don't have a complete outer shell on their own, now we can draw a skeletal formula very similar to what we do for our hydrocarbons just F F every time you see a line in the skeletal formula that is a covalent bond now, why do fluorinesdon't they rotate in triplets?

Well, they already have seven electrons, so they only need to get one. electron from another ring sharing it to be satisfied, let's draw this. Often fluorine has one, two, three, four, five, six seven electrons and the other fluorine also has seven, but we know that one of these will be shared, so let's just check now if this fluorine on the left has a complete outer shell of electrons one two three four five six seven eight yes, this one here one two three four five six seven eight yes, it does it by just sharing one electron each, now they have a complete outer shell of electrons each, for so every time you have a covalent bond you always have a pair of dot crossing electrons, that will always be the case.

Here's a quick little tip to help you remember how many links something needs. to produce as many electrons needed that are equal to the number of bonds formed, let's look at all the group seven elements, the halogens, they all need one more electron to have a full outer shell of eight, so they all form a bond. Group six, usually Talking about oxygen and sulfur, they have six electrons in their outer shell, so they need to gain two Tron, so they both make two bonds: nitrogen and phosphorus, there in group five, they both need to make three bonds, finally, carbon, it's in group four, you actually need it. to make four links to have a complete outer layer, what is the name of the telephone company?

Oh, two named after oxygen gas, oxygens also circulate in pairs, but wait a minute, it's in group six, so it needs to make two bonds. We are absolutely right and that is why if we draw the skeletal formula of oxygen we need a double bond between them. Oxygen actually needs to make two bonds if we were to draw the Don's cross diagram of this now, like we said every time we see a covalent. bond has to be a dot and through a pair of electrons, so we know there's a double bond here, so we know we're going to have a cross dot, a cross dot, there's two pairs of electrons there, let's complete the rest with oxygen one, two, three. four five six seven eight now has a complete outer shell and the same for the other oxygen as well.

What happens to ammonia? Ammonia is nh3, so we have nitrogen in the middle. Which group is in group five? How many electrons does one not need? two three and therefore it will form three covalent bonds, it will always form three covalent bonds and in this case it forms them with hydrogen, we know that it will look like this skeletal formula that you have awakened, so we will never have a cross stitch cross stitch cross stitch are happy the hydrogens, yeah, because they only need one more electron to have a full outer shell there, the element that bucks the trend, they don't need eight, they just need more, let's check the nitrogen one, two, three four five six and then just we need seven eight and the five nitrogen electrons are there let's try methane ch4 carbon in the middle four hydrogens around the outside because which group is carbon in group four so it needs to make four bonds and again they have four bonds so that each bond must have a pair of dot crossed electrons, hydrogen is happy, yes each has two electrons, now carbon one, two, three, four and the four extra electrons of hydrogen, now it has a complete outer shell of eight. let's make one more let's make carbon dioxide co2 we know carbon is in group four so it needs to form four bonds so actually carbon dioxide if you draw the skeletal formula it's like carbon in the middle of two oxygens with a double bond to both, let's just check. oxygen needs to make two bonds because it is in group six.

Carbon needs to make four bonds because it is in group four. That's right, let's try to draw this. We know we have a double bond on each side so we have to have two pairs of electrons crossed by dots so the carbon is happy because one two three four five six seven eight but then we have to finish off our oxygens one two three four one two three four so the trick is not to forget that once you've drawn your dot and cross diagram, just check to see if each of your atoms has a full outer shell of electrons.

You can guarantee that on your exam you will have to draw a dot-cross diagram and it will be worth a couple of points. so it's worth understanding now that we've drawn a bunch of molecules there, that type of bond is called a simple covalent bond, which is a simple covalent structure, something like methane, carbon dioxide, oxygen, however, you can also get giant covalent structures, so when you have a diamond that is effectively a giant molecule that's a little crazy, isn't it? So what does that mean to give in inside? Well, that means okay, we have a bunch of newly bonded carbons.

I'm going to draw this 3d, you won't. We have to draw it in 3D, we have one carbon, we know that it is bonded to four other carbons, but each of them is bonded to four other carbons and each of them is bonded to four other carbons, and so on, so effectively , with which we end. In the end what we find is a giant tetrahedral that has the shape of the bond network of carbon atoms and that is what we call a giant molecular structure. Another example of this is graphite. Graphite is strange because it almost goes against the trend, so we have all the carbons bonded together. others like that, but can you see how many bonds each carbon forms?

I haven't drawn the ones that come off here, but if I did draw them, they come out like this, each carbon is bonded to three more carbons hmm, this is what happens if we have some layers of these carbons bonded to more three carbons, something is actually happening strange, we have the extra electrons that are not used to bond the shells together, so these are intermolecular bonds due to delocalized electrons, so if these shells are weakly bonded together, what does that mean? It means that the layers can slide over each other easily, what is that? Well, let's get four pencils, let's also get four lubricants, so there are a couple of uses for graphite because we have these weak intermolecular bonds due to delocalization. electrons between the layers and that's bonding in a nutshell.

If you have any questions or suggestions about what you would like to see next, please leave a comment below if you found this video helpful and be sure to leave a like and me. I'll see you next time