Understanding Chemical Bonds and Naming Compounds

This is the last presentation for the homework quiz number two slot notes. I have a tendency to combine both 2.6 and 2.7 together because I think they kind of match up to each other. Some textbooks put them together in one section, some split them apart. I just find that when I get done with 2.6, if we just roll into the 2.7, which is... So I think it makes a little bit more sense to combine the two of these together. So first we need to talk about chemical bonds. We've talked about atoms and we've talked about how to do their formulas. And so what we find is those atoms, when they gain or lose electrons, sometimes like to attach to each other or sometimes like they like to share those electrons. So molecules are groups of atoms chemically bonded that contain no... net charge. And they either do this by covalent bonds or ionic bonds. So we're going to take a look at ionic bonds first. Remember we talked about a positively charged ion is a cation, and a negatively charged ion is an anion. And so what we find is because they absolutely lose their electrons and absolutely have positive and negative bonds, or negative charges and opposite charges attract, they absolutely like to stick to each other. So the they're much stronger than covalent bonds. So if you can see in the animation below, notice the sodium's losing an electron, the fluorine picks it up, and then when they become positive and negative, they stick to each other. So like I said, when atoms or molecules lose or gain electrons, they form charged particles. Again, positively charged ions or cations. Negatively charged ions are called anions. Again, there's no change in the number of protons in the nucleus when an ion forms. That would be a nuclear reaction and that's the last type of reaction or the last topic we cover in this course. So we're going to take a look at ionic and we're going to take a look at the most classic ionic. compound which is sodium chloride which is table salt or simple salt. You need to realize anything that has ions in it technically is called a salt. And so if we take a look at sodium chloride, the sodium and the chlorine atoms, the sodium are red and the chlorine are silver, and they form a perfectly cubic shape, a crystalline shape. So what we find is ionic compounds again like i said are held together by strong forces that electrostatic attraction of positives and negatives um and so compounds are usually solids at room temperature like table salt they have a high melting point it's really hard to get salt to melt in a pan if you put it on the stove and it they dissolve quite readily in water okay some aren't more on that details when we get to slot notes for quiz number four And usually what we find is the most common elements are elements from the first two columns, sometimes aluminum, and then this group of light blue on the right hand side. So again, the most reactive metals are green and the most reactive non-metals, because remember you put that stair step line. So when we write formulas for these, we used to do this a really crazy way. until about 1987, 88. And I remember seeing this in a chemistry textbook when I first started teaching, going, wow, that's a really cool idea. And what they said is, or what they showed is, if we take the numbers from the superscript and we crisscross them, what we do is we end up with a compound that's neutral. So the charge on the cation becomes the subscript on the anion, and the charge on the anion becomes the subscript on the cation. I just call this crisscrossing. Crisscross the charges. And then because we want empirical formulas for all our ionic compounds, we need to simplify. And we kind of did that a little bit. We're taking a look at formulas. So the best way to do this is for us to actually just take a look at some examples. So if I've got lithium bromide, that's lithium and bromine, we'll talk about that IBE when we talk about naming compounds. I'm going to go to the periodic table. I'm going to find lithium, and it's in the first column, and it's got a plus one. And the bromine's in column number 17, so it should have a minus one. And the crisscross method says to take the numbers and crisscross the numbers. And then if we need to, to simplify. Well, chemists are efficient, lazy. I don't know, whichever way you want to put it. If we already have one of them, there's no need to put a subscript of a one. So we're going to simplify this by dropping the ones off of it. Technically, both of these formulas are correct. The LIBR without the ones is just chemically more mature. Like I said, both, and I wouldn't give you both of these on a quiz or a test or an exam and ask you the difference, which one's more correct. I would give you the one at the bottom, which is the LIBR. And you'll see that on the quizzes that you're doing for each set of slide notes. So let's switch this up a little bit. We've got now barium, and it's got a plus two if you look right at the top of the column on your periodic table. And chlorine's got a minus one, and the crisscross says, crisscross the number, but remember I dropped the one because I'm just, I'm lazy. I don't want to have to keep writing a bunch of ones. Okay, my handwriting's bad enough. I'd probably end up thinking it was B-A-L, and so we end up with B-A-C-L too. should be pretty simple pretty straightforward then we got calcium oxide so that means take calcium which is plus two and oxygen that's minus two i'm getting these charges by finding the elements on the periodic table and going straight to the top and so when i crisscross the charges i end up with a ca2 o2 but remember it has to be simplified we don't do this very often so we've got to remember to do it because we don't do it very often and so I would technically simplify to CaO so if you notice we'll take aluminum which is plus three and the sulfur sulfide is just sulfur is minus two And we crisscross the charges and we end up with Al2S3. The whole point behind doing this is 2 times plus 3 is plus 6. 3 times a negative 2 is a minus 6. A plus 6 and a minus 6 means it's neutral. It's equal to 0. So this is just a simple way or method of coming up with the correct formula so that we have balanced formula so that our balanced formulas come up with the charge of 0. Well, the other thing is, is lithium's plus one, but if you notice, this is sulfate, not sulfide. So if you go and look on the backside of your periodic table, what you'll find is there is a chart of polyatomic ions. And if you look up sulfate, it says it's SO4 2-. That's where I'm getting that minus 2 from. Remember, we talked about it doesn't matter which side the negative sign goes on. And so if you'll notice, the 1's going to drop down, so we don't write it. And because the sulfate has a 2 minus or minus 2 charge, we're going to drop the 2, and we end up with Li2SO4. So be careful that you don't pick up elements for polyatomic ions and polyatomic ions for elements. Number 14, we've got magnesium hydroxide. The hydroxide is a polyatomic ion. That's why I've got the OH of magnesiums plus two. And if you'll notice, we need two hydroxides, but we're not going to take the O multiplied by two and the H multiplied by two. We're just going to put it around parentheses to show that we need a total of two of the OHs. And then of course, the one goes on the magnesium. for iron 3 sulfate this is interesting in that we've got iron in this roman numeral and sometimes you'll see them in parentheses and sometimes you won't but the roman numeral says pick iron with a plus three charge it's a transition metal we don't even have a charge above it on our periodic table and so we're going to take the iron three and now we know with the sulfate okay so4 two minus We need to crisscross these, but remember we're going to need two for the iron, but we need three sulfates. So we're just going to put it in parentheses and put a three on the outside. So when naming ionic compounds, we've got monatomic ions. And if it was in column one or column two or column 13, we already have a plus on one, a plus two and a plus three. But if you'll notice, you were told to use iron III on the previous example. Well, sometimes iron can be a plus two. So we need to know which Roman numeral to use when we go to name our compounds. And so what we need to do is we need to figure out how to name our compounds and deal with this idea of multiple charges for. our transition metals. So our anions are pretty simple in that all we do is change them to IDE. And if you look on when we were doing all our examples, all the ones that we used a single element for ended in IDE. The only one that wasn't was hydroxide. So please be careful. Hydroxide is not hydrogen, oxygen. It's oxygen, hydrogen, or hydroxide. Okay, polyatomic ions names are not changed unless they're found in an acid and we'll cover that at the very end of this. There's a simple rule for following that, but that lets us know it's an acid or that specific type of compound. So let's start take a look at naming compounds. Let's go with NaCl, so something you're familiar with and something that you can kind of reference to. We got Na and Cl and that's sodium and chlorine. But because this is a compound, not a mixture, we change the ending to ide. If we said sodium chlorine, it means it's a mixture, even though that's never going to happen. Sodium chloride means it's a compound. We got K2S. K is potassium, sulfur, and then we change it to sulfide. Okay, so if you'll notice in this formula, we've got three different elements, but our compounds are binary, which means they have two. Well, the Na should look familiar because that's sodium, like from sodium chloride. And then you're going to need to find the polyatomic ion. So if you look on the chart on the backside of your periodic table, NO3 is nitrate. So this becomes sodium nitrate. And so in this one, we've got CO3, so that's carbonate. So this becomes potassium carbonate. I'm not going to ask you to memorize these polyatomic ions, but you're going to need to become familiar with them just by doing the quizzes and the practice problems and filling in your slot nodes. You're going to see a lot of these and you're going to go, oh, I think I remember seeing that as one of those polyatomic ions. Let me go check on the backside of the periodic table. Magnesium, oh, we got an OH. Oh, the parentheses is a big clue that it's a polyatomic ion. So we find OH is hydroxide. And so we end up with magnesium hydroxide. The problem is, is we have binary ionic compounds for the transition metal, and they need a Roman. Numeral. Now for zinc and silver, we don't need to because they only have a charge of plus one. And so and sometimes the metalloids and we're not going to get too hung up on those. I'm not going to put those as test questions and try and trick you into getting something wrong. But we need to know how to come up with these charges and the Roman numerals. So if we take a look, there's a set of rules for assigning oxidation numbers. And you notice how I keep saying minus and the plus sign can go on either side. Well, the reason is, is if it says it's minus one, it's got a charge of minus one. If it's got a one minus, that actually means one electron is lost. If it's a plus one, it's got a plus one charge. If it's one plus, it means one electron is lost. So, but we don't have to get too hung up on those charges and the directions that it's moving because we don't cover electrochemistry until the second half of Chem 104. So that's why we can just kind of treat the positive and the negative sign on either side as basically the same thing, okay? Well, rule number one, we're not gonna really worry about in here either because- We're not going to use this in chemical equations. We're going to use it in formula. But rule one says that elements all behind by themselves and the diatomic elements such as O2 and P4 and S8, we talked about the O2 and the S8, they're going to have an oxidation number of zero. Not going to have to worry about that in this class because we don't, right now, because we don't assign it to reactions. Okay. Rule number two is oxygen is a negative two. except in peroxides, but it'll show itself. Hygiene rule number three is going to be a plus one. Rule number four, you've already put at the top of your periodic table because you said group one's plus one. Group two is plus two. Group 17 is minus one. And that's unless it's bound to oxygen, then it's going to be a plus one. Again, that'll reveal itself if we follow the rules. I'll show you what I mean. I got a couple examples coming up. So the sum of the oxidation numbers equals zero if it's in a compound. That's why we've been crisscrossing the charges. So technically they're oxidation numbers too. Or the charge of the polyatomic ion. And we started to take a look at those on a couple of compounds. So with only a very few exceptions, we can use these rules. Sometimes they're expanded out into a longer list and then they start putting more complex examples. Well, we don't need that at this level, not in Chem 103. If there's a complex example, what you'll notice if you were ever to use it, you'd realize these rules aren't finding the right answer to it. And then you would have to go and look up the longer set of rules. So it says, what is the oxidation number of hydrogen and chlorine in HCl? Well, this you could probably just go to your periodic table, but I want to show you a method for doing this. And so if we look at the individual charges, hydrogen is plus one because of rule number three, oxygen's minus two, hydrogen's plus one. And chlorine is going to be minus one because it's in group number 17. But remember I told you the reason we're writing these formulas and we're crisscrossing the charges is so that the total charge is equal to zero. So one minus a negative one, one times a plus one, and a plus one plus a minus one equals zero. So we used to do this for every single compound instead of just crisscrossing the charges. We didn't have to worry. We technically wouldn't have to do this for HCL because the charges are already on the periodic table. The individual charges are plus one and minus one, respectively. And like I said, you already have those listed at the top of the columns on your periodic table. So let's look at another example that we could probably get off the periodic table. But I want to show you what's called going around the block. So we've already established in rule number two that oxygen is minus two. So one times a negative two is a negative two. So our total charge is minus two for our oxygen. Well, I need to add plus two and a minus two equals zero. If I divide that by two, I end up with a plus one. And if you'll notice, this is the same charge as you would have on the periodic table. Okay, so let's do something a little bit different. First of all, if you'll notice this, that the chlorine and the oxygen, well, I could just go to the periodic table, but notice that negative one, which means our total charges aren't going to equal zero. And so if we do the individual charge, we're going to start out with the oxygen because we always start at the top of the list. And so oxygen's minus two. Total charge on oxygen is minus two, but we're not going to equal zero. We're going to equal minus one, which is the charge on this polyatomic ion. So a plus one and a minus two gives us a minus one, which is really interesting because if you'll notice the chlorine is now plus one, not minus one, like you would have predicted from the periodic table. So let's take a look at a couple things that you can do with this. If you'll notice, we now have three elements, but we can still follow our rules. Individual charge for oxygen is minus two. Four times a negative two is a, sorry, and then the potassium is going to be a plus one. I forgot to put that animation there. And we got those off the periodic table, but manganese is a transition metal. And so the total charge, four times a negative two. is a negative eight and this has got to equal zero well potassium is a plus one so what fits in the middle well plus one and minus eight makes a minus seven so the manganese needs to be a plus seven which means the individual charge on the manganese is plus seven what's get what gets interesting is sometimes when you do this you can actually end up with oxidation numbers that are Again, that's that more extensive rules. We're just going to stick with the basic ones, and I'm not going to give you any ones that have fractions in them. So oxygens minus 2, potassiums plus 1, manganese is plus 7. So the reason we were doing this is so we can find the Roman numerals. So it says, what is the name of an ion? Well, we got to first find out because nickel is a transition metal. We don't have a charge above it. So oxygen is minus 2. So what plus a minus 2 will equal 0? And that's a plus 2. So the individual charge on the nickel is plus 2, which means we're going to need a Roman numeral 2 for nickel. And so we're going to end up with nickel oxide. Normally we don't underline that, just underlined it for emphasis on this slide. If we've got Fe2O3, iron's a transition metal, so we have the individual charges. Oxygen's always minus two, so three times a minus two is a minus Six. Well, what plus a minus six equals zero? A plus six. Well, if you notice, we've got two irons. So each individual iron is going to be plus three. So we're going to need a Roman numeral three for this name. And we're going to end up with iron three oxide. Well, you guys don't call it iron three oxide. You guys just call it rust. Okay. Rust is iron three oxide. Okay, again, the underline under the three is just there for emphasis. We typically don't write just put an underline underneath the three. So now we've got Cu2O. Let's see, oxygens minus two, one times a negative two. And what plus a negative two equals zero? Well, that's plus two. Don't forget there's two coppers, so we need to divide that by two. And we end up with a Roman numeral one. So we end up with copper one oxide. Now the hard part's over because now we're going to go name things that have covalent bonds or molecular compounds. So... covalent bonds are formed by sharing a pair of electrons so they involve two or more non-metals so if it's got a metal we follow all the stuff we've just talked about gotta sometimes put a roman numeral we crisscross the charges change the ending to ide and when these pairs of electrons are shared it can be a single a double or a triple more detail on that a little bit after we get done with the midterm So what we find is a molecule is an aggregate of two or more atoms. Okay, and so here's some ball and stick models and their formulas underneath. And that ball and stick is where we're kind of going to that three-dimensional shape. The shapes are actually linear, bent, trigonal, pyramidal, and tetrahedral. But more on that story after we get done with the midterm. Diatomic molecules contain only two atoms. and polyatomic molecules contain more than two atoms. And so we have ozone instead of oxygen and water and ammonia and the CH4. There are seven atoms that are found to be diatomic in nature. Remember I told you atoms don't like to exist by themselves as atoms. They like to become ions or they like to bond to somebody else. Well, we've got bromine, iodine, nitrogen, chlorine, hydrogen, oxygen, and fluorine. It's kind of, man, that's hard to remember in a row. Well, I worked with another chemistry instructor and he was from Germany. I mean, not from Germany, sorry. He was from Ohio and he lived in an area that had a lot of German people. He went to Ohio State and his professor had a German background. He says, well, that's Brinkelhoff. Sounds like the last name Brinkelhoff. And if you remember that, you can remember which ones are diatomic in nature. So unlike ionic compounds, there's no simple way to deduce the formula of a binary molecular compound because we don't have any charges to drop. So when we name them, what we do is we use a Greek prefix. And so when we go to name, we put a Greek prefix in front of the names of the elements. And then we add the ending IDE to show it's a compound, not a mixture. So before we can do anything with this, we need to make sure we got the right Greek prefixes. And so one is mono, not uno. Two is di. Three is tri. Four is tetra. And five is penta. 6 is hexa, 7 is hepta, 8 is octa, 9 is nona, and 10 is deca, as in decade. So all I have to do is apply the prefixes. And the best way to do this is let's just look at some examples. okay so i've got co which is carbon monoxide in reality remember how we didn't write the ones well we don't write mono very often the only reason we write carbon monoxide is the difference between carbon monoxide and carbon dioxide is carbon monoxide is deadly carbon dioxide is antagonistic what that means is carbon monoxide will kill you carbon dioxide pretty much will just make you sick okay unless you get too much carbon dioxide you don't die that you die because it replaces it gets in the way of the oxygen in whatever you're breathing okay so2 sulfur dioxide notice i don't use the mono ending ide P2S3 is diphosphorus trisulfide. So we have one nitrogen and three fluorines, so this becomes nitrogen trifluoride. This one has two nitrogens and an oxygen. so it's dinitrogen oxide sometimes in the racing world it'll be called dinitrogen monoxide or dmo or it's also called nitrous oxide that's the old name or if you go to the dentist office he's not gonna it may call it nitrous oxide or you may just call it laughing gas nitrogen with three hydrogens is nitrogen trihydride, but if you go to Walmart to buy a bottle of something to clean your windows, it's probably not going to say it's got nitrogen trihydride in it. It's probably going to say it's got ammonia if it's an ammonia-based cleaner. H2O could be dihydrogen monoxide, and that's interesting to look up, and there's a bunch of stories about kids trying to get it banned. couple other things, but we're not going to call it dihydrogen monoxide. We're just simply going to call it water. So the last thing we need to take a look at are acids, and acids donate hydrogen ions to water. And so if I add HCl to water, I end up with hydrogen ions and chlorine ions or hydronium ions more on that story a little later in the semester so i end up with hydrochloric acid and we'll recognize most acids because they begin with a hydrogen so acid's not containing any oxygen used to prefix hydro the root of the anion's element name and the suffix ic so we end up with hydrochloric acid and so if it's H2S is hydrosulfuric acid or sulfic acid sorry about that hydrosulfic acid if it contains oxy acids the root of the anion's name that the anion originally ended in 8 like nitrate it becomes nitric if the anion originally ended in ite this is the polyatomic ions we change it to alce the nice thing is this alphabetically matches up eight becomes ic and i becomes alce so we've got sulfuric acid the carbonate hydrogen carbonate becomes carbonic acid and the SO3 sulfite so it becomes sulfurous acid When we go to name bases, they contain hydroxide ions in them. So we just follow the rules we've already had for naming polyatomic ions. So it'd be sodium hydroxide, magnesium hydroxide. So let's take a look at a couple examples. KCl is ionic, has a metal. The NCL3 does not have any metals, so it's covalent, has all non-metals. ICL has all non-metals, so it's covalent, so you would need prefixes when you go to name those. MGCL2, magnesium's a metal, so it's ionic, so you would just name that as magnesium chloride. And here we just want to crisscross the charges. Got to remember to simplify the twos. ALBR 3. And then remember when we go to crisscross, we need to put that phosphate in parentheses before we put the two on it. says name the font well cscl that's a metal so that just becomes cesium chloride k2s we've seen that that's potassium sulfide hbr is hydrogen bromide but if we were to drop this into water it would become an acid and we call it hydrobromic acid like i said we're not going to worry too much about the naming of acids because We're going to come back and look at acids very directly after the midterm. 53 is just asking you to write the formulas. So rubidium bromide should be RBBR. Sodium oxide should be Na2O because there was a minus 2 charge on the oxygen. Hydrogen fluoride is HF. Then we need to do chlorine. That's pretty simple. It says take chlorine and add two oxygens to it. Potassium phosphide, be careful that's not the polyatomic ion, that's just phosphorus because it's ending in ide, just ide directly. So it's K3P. E is asking you to combine aluminum and nitrogen so you end up with Aln because aluminum's plus three and nitrogen's minus three. Number 59, the following ionic, write the formulas for each compound. So copper 2 sulfate, which says take the copper with a plus 2 and add the SO4 to it. Titanium dioxide, you're going to find in sunscreen. And sodium bisulfate, you got to be careful when you look on those chart of polytomic ionics. There's a couple of them that are a little bit exotic. And so we end up with NAHSO4. And this ends the last section for quiz number two.

I just find that when I get done with 2.6, if we just roll into the 2.7, which is... So I think it makes a little bit more sense to combine the two of these together. So first we need to talk about chemical bonds. We've talked about atoms and we've talked about how to do their formulas. And so what we find is those atoms, when they gain or lose electrons, sometimes like to attach to each other or sometimes like they like to share those electrons.

So molecules are groups of atoms chemically bonded that contain no... net charge. And they either do this by covalent bonds or ionic bonds. So we're going to take a look at ionic bonds first. Remember we talked about a positively charged ion is a cation, and a negatively charged ion is an anion.

And so what we find is because they absolutely lose their electrons and absolutely have positive and negative bonds, or negative charges and opposite charges attract, they absolutely like to stick to each other. So the they're much stronger than covalent bonds. So if you can see in the animation below, notice the sodium's losing an electron, the fluorine picks it up, and then when they become positive and negative, they stick to each other. So like I said, when atoms or molecules lose or gain electrons, they form charged particles. Again, positively charged ions or cations.

Negatively charged ions are called anions. Again, there's no change in the number of protons in the nucleus when an ion forms. That would be a nuclear reaction and that's the last type of reaction or the last topic we cover in this course.

So we're going to take a look at ionic and we're going to take a look at the most classic ionic. compound which is sodium chloride which is table salt or simple salt. You need to realize anything that has ions in it technically is called a salt. And so if we take a look at sodium chloride, the sodium and the chlorine atoms, the sodium are red and the chlorine are silver, and they form a perfectly cubic shape, a crystalline shape. So what we find is ionic compounds again like i said are held together by strong forces that electrostatic attraction of positives and negatives um and so compounds are usually solids at room temperature like table salt they have a high melting point it's really hard to get salt to melt in a pan if you put it on the stove and it they dissolve quite readily in water okay some aren't more on that details when we get to slot notes for quiz number four And usually what we find is the most common elements are elements from the first two columns, sometimes aluminum, and then this group of light blue on the right hand side.

So again, the most reactive metals are green and the most reactive non-metals, because remember you put that stair step line. So when we write formulas for these, we used to do this a really crazy way. until about 1987, 88. And I remember seeing this in a chemistry textbook when I first started teaching, going, wow, that's a really cool idea. And what they said is, or what they showed is, if we take the numbers from the superscript and we crisscross them, what we do is we end up with a compound that's neutral. So the charge on the cation becomes the subscript on the anion, and the charge on the anion becomes the subscript on the cation.

I just call this crisscrossing. Crisscross the charges. And then because we want empirical formulas for all our ionic compounds, we need to simplify.

And we kind of did that a little bit. We're taking a look at formulas. So the best way to do this is for us to actually just take a look at some examples. So if I've got lithium bromide, that's lithium and bromine, we'll talk about that IBE when we talk about naming compounds.

I'm going to go to the periodic table. I'm going to find lithium, and it's in the first column, and it's got a plus one. And the bromine's in column number 17, so it should have a minus one.

And the crisscross method says to take the numbers and crisscross the numbers. And then if we need to, to simplify. Well, chemists are efficient, lazy.

I don't know, whichever way you want to put it. If we already have one of them, there's no need to put a subscript of a one. So we're going to simplify this by dropping the ones off of it.

Technically, both of these formulas are correct. The LIBR without the ones is just chemically more mature. Like I said, both, and I wouldn't give you both of these on a quiz or a test or an exam and ask you the difference, which one's more correct.

I would give you the one at the bottom, which is the LIBR. And you'll see that on the quizzes that you're doing for each set of slide notes. So let's switch this up a little bit.

We've got now barium, and it's got a plus two if you look right at the top of the column on your periodic table. And chlorine's got a minus one, and the crisscross says, crisscross the number, but remember I dropped the one because I'm just, I'm lazy. I don't want to have to keep writing a bunch of ones.

Okay, my handwriting's bad enough. I'd probably end up thinking it was B-A-L, and so we end up with B-A-C-L too. should be pretty simple pretty straightforward then we got calcium oxide so that means take calcium which is plus two and oxygen that's minus two i'm getting these charges by finding the elements on the periodic table and going straight to the top and so when i crisscross the charges i end up with a ca2 o2 but remember it has to be simplified we don't do this very often so we've got to remember to do it because we don't do it very often and so I would technically simplify to CaO so if you notice we'll take aluminum which is plus three and the sulfur sulfide is just sulfur is minus two And we crisscross the charges and we end up with Al2S3.

The whole point behind doing this is 2 times plus 3 is plus 6. 3 times a negative 2 is a minus 6. A plus 6 and a minus 6 means it's neutral. It's equal to 0. So this is just a simple way or method of coming up with the correct formula so that we have balanced formula so that our balanced formulas come up with the charge of 0. Well, the other thing is, is lithium's plus one, but if you notice, this is sulfate, not sulfide. So if you go and look on the backside of your periodic table, what you'll find is there is a chart of polyatomic ions. And if you look up sulfate, it says it's SO4 2-. That's where I'm getting that minus 2 from.

Remember, we talked about it doesn't matter which side the negative sign goes on. And so if you'll notice, the 1's going to drop down, so we don't write it. And because the sulfate has a 2 minus or minus 2 charge, we're going to drop the 2, and we end up with Li2SO4.

So be careful that you don't pick up elements for polyatomic ions and polyatomic ions for elements. Number 14, we've got magnesium hydroxide. The hydroxide is a polyatomic ion.

That's why I've got the OH of magnesiums plus two. And if you'll notice, we need two hydroxides, but we're not going to take the O multiplied by two and the H multiplied by two. We're just going to put it around parentheses to show that we need a total of two of the OHs.

And then of course, the one goes on the magnesium. for iron 3 sulfate this is interesting in that we've got iron in this roman numeral and sometimes you'll see them in parentheses and sometimes you won't but the roman numeral says pick iron with a plus three charge it's a transition metal we don't even have a charge above it on our periodic table and so we're going to take the iron three and now we know with the sulfate okay so4 two minus We need to crisscross these, but remember we're going to need two for the iron, but we need three sulfates. So we're just going to put it in parentheses and put a three on the outside. So when naming ionic compounds, we've got monatomic ions. And if it was in column one or column two or column 13, we already have a plus on one, a plus two and a plus three.

But if you'll notice, you were told to use iron III on the previous example. Well, sometimes iron can be a plus two. So we need to know which Roman numeral to use when we go to name our compounds. And so what we need to do is we need to figure out how to name our compounds and deal with this idea of multiple charges for. our transition metals.

So our anions are pretty simple in that all we do is change them to IDE. And if you look on when we were doing all our examples, all the ones that we used a single element for ended in IDE. The only one that wasn't was hydroxide. So please be careful. Hydroxide is not hydrogen, oxygen.

It's oxygen, hydrogen, or hydroxide. Okay, polyatomic ions names are not changed unless they're found in an acid and we'll cover that at the very end of this. There's a simple rule for following that, but that lets us know it's an acid or that specific type of compound. So let's start take a look at naming compounds. Let's go with NaCl, so something you're familiar with and something that you can kind of reference to.

We got Na and Cl and that's sodium and chlorine. But because this is a compound, not a mixture, we change the ending to ide. If we said sodium chlorine, it means it's a mixture, even though that's never going to happen. Sodium chloride means it's a compound.

We got K2S. K is potassium, sulfur, and then we change it to sulfide. Okay, so if you'll notice in this formula, we've got three different elements, but our compounds are binary, which means they have two. Well, the Na should look familiar because that's sodium, like from sodium chloride.

And then you're going to need to find the polyatomic ion. So if you look on the chart on the backside of your periodic table, NO3 is nitrate. So this becomes sodium nitrate.

And so in this one, we've got CO3, so that's carbonate. So this becomes potassium carbonate. I'm not going to ask you to memorize these polyatomic ions, but you're going to need to become familiar with them just by doing the quizzes and the practice problems and filling in your slot nodes.

You're going to see a lot of these and you're going to go, oh, I think I remember seeing that as one of those polyatomic ions. Let me go check on the backside of the periodic table. Magnesium, oh, we got an OH. Oh, the parentheses is a big clue that it's a polyatomic ion. So we find OH is hydroxide.

And so we end up with magnesium hydroxide. The problem is, is we have binary ionic compounds for the transition metal, and they need a Roman. Numeral.

Now for zinc and silver, we don't need to because they only have a charge of plus one. And so and sometimes the metalloids and we're not going to get too hung up on those. I'm not going to put those as test questions and try and trick you into getting something wrong. But we need to know how to come up with these charges and the Roman numerals. So if we take a look, there's a set of rules for assigning oxidation numbers.

And you notice how I keep saying minus and the plus sign can go on either side. Well, the reason is, is if it says it's minus one, it's got a charge of minus one. If it's got a one minus, that actually means one electron is lost.

If it's a plus one, it's got a plus one charge. If it's one plus, it means one electron is lost. So, but we don't have to get too hung up on those charges and the directions that it's moving because we don't cover electrochemistry until the second half of Chem 104. So that's why we can just kind of treat the positive and the negative sign on either side as basically the same thing, okay?

Well, rule number one, we're not gonna really worry about in here either because- We're not going to use this in chemical equations. We're going to use it in formula. But rule one says that elements all behind by themselves and the diatomic elements such as O2 and P4 and S8, we talked about the O2 and the S8, they're going to have an oxidation number of zero. Not going to have to worry about that in this class because we don't, right now, because we don't assign it to reactions. Okay.

Rule number two is oxygen is a negative two. except in peroxides, but it'll show itself. Hygiene rule number three is going to be a plus one. Rule number four, you've already put at the top of your periodic table because you said group one's plus one. Group two is plus two.

Group 17 is minus one. And that's unless it's bound to oxygen, then it's going to be a plus one. Again, that'll reveal itself if we follow the rules.

I'll show you what I mean. I got a couple examples coming up. So the sum of the oxidation numbers equals zero if it's in a compound. That's why we've been crisscrossing the charges.

So technically they're oxidation numbers too. Or the charge of the polyatomic ion. And we started to take a look at those on a couple of compounds.

So with only a very few exceptions, we can use these rules. Sometimes they're expanded out into a longer list and then they start putting more complex examples. Well, we don't need that at this level, not in Chem 103. If there's a complex example, what you'll notice if you were ever to use it, you'd realize these rules aren't finding the right answer to it. And then you would have to go and look up the longer set of rules. So it says, what is the oxidation number of hydrogen and chlorine in HCl?

Well, this you could probably just go to your periodic table, but I want to show you a method for doing this. And so if we look at the individual charges, hydrogen is plus one because of rule number three, oxygen's minus two, hydrogen's plus one. And chlorine is going to be minus one because it's in group number 17. But remember I told you the reason we're writing these formulas and we're crisscrossing the charges is so that the total charge is equal to zero.

So one minus a negative one, one times a plus one, and a plus one plus a minus one equals zero. So we used to do this for every single compound instead of just crisscrossing the charges. We didn't have to worry.

We technically wouldn't have to do this for HCL because the charges are already on the periodic table. The individual charges are plus one and minus one, respectively. And like I said, you already have those listed at the top of the columns on your periodic table.

So let's look at another example that we could probably get off the periodic table. But I want to show you what's called going around the block. So we've already established in rule number two that oxygen is minus two.

So one times a negative two is a negative two. So our total charge is minus two for our oxygen. Well, I need to add plus two and a minus two equals zero. If I divide that by two, I end up with a plus one. And if you'll notice, this is the same charge as you would have on the periodic table.

Okay, so let's do something a little bit different. First of all, if you'll notice this, that the chlorine and the oxygen, well, I could just go to the periodic table, but notice that negative one, which means our total charges aren't going to equal zero. And so if we do the individual charge, we're going to start out with the oxygen because we always start at the top of the list. And so oxygen's minus two.

Total charge on oxygen is minus two, but we're not going to equal zero. We're going to equal minus one, which is the charge on this polyatomic ion. So a plus one and a minus two gives us a minus one, which is really interesting because if you'll notice the chlorine is now plus one, not minus one, like you would have predicted from the periodic table.

So let's take a look at a couple things that you can do with this. If you'll notice, we now have three elements, but we can still follow our rules. Individual charge for oxygen is minus two.

Four times a negative two is a, sorry, and then the potassium is going to be a plus one. I forgot to put that animation there. And we got those off the periodic table, but manganese is a transition metal. And so the total charge, four times a negative two. is a negative eight and this has got to equal zero well potassium is a plus one so what fits in the middle well plus one and minus eight makes a minus seven so the manganese needs to be a plus seven which means the individual charge on the manganese is plus seven what's get what gets interesting is sometimes when you do this you can actually end up with oxidation numbers that are Again, that's that more extensive rules.

We're just going to stick with the basic ones, and I'm not going to give you any ones that have fractions in them. So oxygens minus 2, potassiums plus 1, manganese is plus 7. So the reason we were doing this is so we can find the Roman numerals. So it says, what is the name of an ion? Well, we got to first find out because nickel is a transition metal. We don't have a charge above it.

So oxygen is minus 2. So what plus a minus 2 will equal 0? And that's a plus 2. So the individual charge on the nickel is plus 2, which means we're going to need a Roman numeral 2 for nickel. And so we're going to end up with nickel oxide. Normally we don't underline that, just underlined it for emphasis on this slide. If we've got Fe2O3, iron's a transition metal, so we have the individual charges.

Oxygen's always minus two, so three times a minus two is a minus Six. Well, what plus a minus six equals zero? A plus six. Well, if you notice, we've got two irons.

So each individual iron is going to be plus three. So we're going to need a Roman numeral three for this name. And we're going to end up with iron three oxide.

Well, you guys don't call it iron three oxide. You guys just call it rust. Okay.

Rust is iron three oxide. Okay, again, the underline under the three is just there for emphasis. We typically don't write just put an underline underneath the three.

So now we've got Cu2O. Let's see, oxygens minus two, one times a negative two. And what plus a negative two equals zero? Well, that's plus two.

Don't forget there's two coppers, so we need to divide that by two. And we end up with a Roman numeral one. So we end up with copper one oxide. Now the hard part's over because now we're going to go name things that have covalent bonds or molecular compounds. So...

covalent bonds are formed by sharing a pair of electrons so they involve two or more non-metals so if it's got a metal we follow all the stuff we've just talked about gotta sometimes put a roman numeral we crisscross the charges change the ending to ide and when these pairs of electrons are shared it can be a single a double or a triple more detail on that a little bit after we get done with the midterm So what we find is a molecule is an aggregate of two or more atoms. Okay, and so here's some ball and stick models and their formulas underneath. And that ball and stick is where we're kind of going to that three-dimensional shape.

The shapes are actually linear, bent, trigonal, pyramidal, and tetrahedral. But more on that story after we get done with the midterm. Diatomic molecules contain only two atoms. and polyatomic molecules contain more than two atoms. And so we have ozone instead of oxygen and water and ammonia and the CH4.

There are seven atoms that are found to be diatomic in nature. Remember I told you atoms don't like to exist by themselves as atoms. They like to become ions or they like to bond to somebody else.

Well, we've got bromine, iodine, nitrogen, chlorine, hydrogen, oxygen, and fluorine. It's kind of, man, that's hard to remember in a row. Well, I worked with another chemistry instructor and he was from Germany.

I mean, not from Germany, sorry. He was from Ohio and he lived in an area that had a lot of German people. He went to Ohio State and his professor had a German background. He says, well, that's Brinkelhoff.

Sounds like the last name Brinkelhoff. And if you remember that, you can remember which ones are diatomic in nature. So unlike ionic compounds, there's no simple way to deduce the formula of a binary molecular compound because we don't have any charges to drop. So when we name them, what we do is we use a Greek prefix. And so when we go to name, we put a Greek prefix in front of the names of the elements.

And then we add the ending IDE to show it's a compound, not a mixture. So before we can do anything with this, we need to make sure we got the right Greek prefixes. And so one is mono, not uno.

Two is di. Three is tri. Four is tetra. And five is penta. 6 is hexa, 7 is hepta, 8 is octa, 9 is nona, and 10 is deca, as in decade.

So all I have to do is apply the prefixes. And the best way to do this is let's just look at some examples. okay so i've got co which is carbon monoxide in reality remember how we didn't write the ones well we don't write mono very often the only reason we write carbon monoxide is the difference between carbon monoxide and carbon dioxide is carbon monoxide is deadly carbon dioxide is antagonistic what that means is carbon monoxide will kill you carbon dioxide pretty much will just make you sick okay unless you get too much carbon dioxide you don't die that you die because it replaces it gets in the way of the oxygen in whatever you're breathing okay so2 sulfur dioxide notice i don't use the mono ending ide P2S3 is diphosphorus trisulfide.

So we have one nitrogen and three fluorines, so this becomes nitrogen trifluoride. This one has two nitrogens and an oxygen. so it's dinitrogen oxide sometimes in the racing world it'll be called dinitrogen monoxide or dmo or it's also called nitrous oxide that's the old name or if you go to the dentist office he's not gonna it may call it nitrous oxide or you may just call it laughing gas nitrogen with three hydrogens is nitrogen trihydride, but if you go to Walmart to buy a bottle of something to clean your windows, it's probably not going to say it's got nitrogen trihydride in it. It's probably going to say it's got ammonia if it's an ammonia-based cleaner.

H2O could be dihydrogen monoxide, and that's interesting to look up, and there's a bunch of stories about kids trying to get it banned. couple other things, but we're not going to call it dihydrogen monoxide. We're just simply going to call it water.

So the last thing we need to take a look at are acids, and acids donate hydrogen ions to water. And so if I add HCl to water, I end up with hydrogen ions and chlorine ions or hydronium ions more on that story a little later in the semester so i end up with hydrochloric acid and we'll recognize most acids because they begin with a hydrogen so acid's not containing any oxygen used to prefix hydro the root of the anion's element name and the suffix ic so we end up with hydrochloric acid and so if it's H2S is hydrosulfuric acid or sulfic acid sorry about that hydrosulfic acid if it contains oxy acids the root of the anion's name that the anion originally ended in 8 like nitrate it becomes nitric if the anion originally ended in ite this is the polyatomic ions we change it to alce the nice thing is this alphabetically matches up eight becomes ic and i becomes alce so we've got sulfuric acid the carbonate hydrogen carbonate becomes carbonic acid and the SO3 sulfite so it becomes sulfurous acid When we go to name bases, they contain hydroxide ions in them. So we just follow the rules we've already had for naming polyatomic ions.

So it'd be sodium hydroxide, magnesium hydroxide. So let's take a look at a couple examples. KCl is ionic, has a metal.

The NCL3 does not have any metals, so it's covalent, has all non-metals. ICL has all non-metals, so it's covalent, so you would need prefixes when you go to name those. MGCL2, magnesium's a metal, so it's ionic, so you would just name that as magnesium chloride.

And here we just want to crisscross the charges. Got to remember to simplify the twos. ALBR 3. And then remember when we go to crisscross, we need to put that phosphate in parentheses before we put the two on it. says name the font well cscl that's a metal so that just becomes cesium chloride k2s we've seen that that's potassium sulfide hbr is hydrogen bromide but if we were to drop this into water it would become an acid and we call it hydrobromic acid like i said we're not going to worry too much about the naming of acids because We're going to come back and look at acids very directly after the midterm.

53 is just asking you to write the formulas. So rubidium bromide should be RBBR. Sodium oxide should be Na2O because there was a minus 2 charge on the oxygen.

Hydrogen fluoride is HF. Then we need to do chlorine. That's pretty simple.

It says take chlorine and add two oxygens to it. Potassium phosphide, be careful that's not the polyatomic ion, that's just phosphorus because it's ending in ide, just ide directly. So it's K3P. E is asking you to combine aluminum and nitrogen so you end up with Aln because aluminum's plus three and nitrogen's minus three.

Number 59, the following ionic, write the formulas for each compound. So copper 2 sulfate, which says take the copper with a plus 2 and add the SO4 to it. Titanium dioxide, you're going to find in sunscreen.

And sodium bisulfate, you got to be careful when you look on those chart of polytomic ionics. There's a couple of them that are a little bit exotic. And so we end up with NAHSO4. And this ends the last section for quiz number two.

Transcript for:Understanding Chemical Bonds and Naming Compounds

Transcript for:
Understanding Chemical Bonds and Naming Compounds