all great movies deserve a sequel and my nomenclature lectures are no exceptions so if you love my ionic nomenclature series get ready for the spin-off series naming binary covalent compounds and original dr kelly production with a capital randomly capitalized first thing we need to do is we need to define what a covalent compound is a covalent compound a covalent compound is a compound held together by covalent bonds and a covalent bond of course is a shared pair of electrons it's a pair of valence electrons that have an equal probability of belonging to the nucleus of two different atoms or has a significant probability of belonging to the nucleus of two different atoms why this definition of a covalent bond is important is that it means that covalence compounds existence is much different than the existence of a ionic compound we talked about how ionic compounds existed as crystals because that force of attraction could go all over the place in 360 degrees in three-dimensional space well when it comes to sharing a pair of electrons that can't happen if two atoms are going to share a pair of electrons the electrons they're going to share are going to need to stay between the two atoms they can't go hither tither and yawn all over the place they got to stay located between the two atoms that means that there is not an unlimited um arrangement around a given atom there's only a specific number of bonds an atom can form not only that but the position of two atoms relative to each other is relatively fixed additionally not only does it limit the number of partners an atom can have but it means that when we look at the formula for an ionic compound we're writing the formula for something that actually exists that's so important i'm going to write it down for you ta-da words magically appearing out of thin air i do magic tricks as well as teach chemistry the formula for a covalent compound represents the formula for a molecule as it actually exists a molecule is the simplest unit of a com of a of a covalent compound not too magical i can't seem to get my writing right but at any rate tadam words magically appearing before your eyes what can i say i not only do chemistry i do magic as well although some people say that chemistry appears magical some people say that the chemistry exude is magical but at any rate the formula for a covalent compound represents the formula for a molecule as it actually exists a molecule is the simplest unit of a compound what do i mean by that and why am i making such a big deal out of that well let's start with what i mean by this what i mean by this is that when i write the formula for water h2o this represents water as it actually exists water actually exists as two oxygen atoms i mean is one oxygen atom attached to two hydrogen atoms when you drink a glass of water you're drinking a collection of little molecules and each one of those little molecules consists of one oxygen atoms atom connected to two hydrogen atoms that's how water actually exists when you turn on your stove and you light natural gas you're lighting methane one carbon connected to four hydrogens that's how it actually exists that gas is a collection of little molecules with one carbon attached to four hydrogens you're like well duh what's the big deal here the big deal is how this differs from ionic compounds remember when we talked about ionic compounds we said that the formula didn't represent something that actually existed when we wrote the formula sodium chloride we said there wasn't any single sodium and chloride ions out there floating around having a party by themselves instead it was just a ratio of things in a crystal when we were dealing with ionic compounds when ionic when we wrote the formula for an ionic compound we're just writing a ratio not something that physically existed for covalent compounds that formula represents something that physically exists not only that but the formula because it represents something that physically exists it's not a ratio the fact that it's not a ratio is important it means that for covalent compounds because the formula for a covalent compound doesn't represent a ratio but represents something that actually exists it means that covalent compounds there that when you're dealing with covalent compounds there can be multiple combinations of just two elements one of the easiest to think of is nitrogen i'm sorry i'm so excited i'm losing control my my ability to speak here i'm i'm beside myself the strange thing is i'm also talking to myself beside myself but anyway nitrogen and oxygen alone can form all sorts of combinations each one of these combinations actually exists and because each one of these combinations actually exists we have to have a nomenclature system that allows us to name these compounds as different compounds that simplistic system we used for ionic compounds won't cut the mustard anymore because it doesn't allow us to name all these pardon me now i got the burps it doesn't allow us to name each one of these compounds individually so we have to develop a system that does fortunately when i say that the system for naming ionic compounds was simplistic that doesn't imply that this this system's any harder matter of fact most students find this the way of naming ionic compounds much much easier to name an ionic compound and let's walk through the process here let's name an ionic compound that you guys already know the answer to my guess is you can already name this compound without knowing without me walking you through the rules to name it but we have this compound here the first thing we're going to do is we're going to verify that we have a covalent compound you will have a covalent compound when you have two metals two non-metals bonded together now the other rule for when you have a covalent compound is the pinky out rule the highfalutin you're having a cup of key with the queen rule is the electronegativity difference the electronegativity difference between the two atoms is less than 1.9 huh what's electronegativity if you're in my class we've covered it in a different lecture if you're not in my class don't worry about it because as i said that's the very formal rule it's much easier and much simpler and it's what everybody does is they simply say that you have a covalent compound whenever you have two non-metals bonded together so if you have a covalent compound that means you have two nonmetals your first step once you've verified you have a covalent compound write the name of the first element so in this case our first element's carbon second step write the name of the second element where the suffix ide so just like we did with ionic compounds we take that second element we drop the last syllable and add ide so our second element here is oxygen so oxygen is going to become oxide so we have carbon then we have oxide then we've got one last step and that's denote the number of each atom using greek prefixes omit the prefix mono on the first element but never the second oh wow that's a loaded third step huh denote the number of each using greek prefixes greek prefixes what greek prefixes how do we suddenly get into the greeks i i thought we were taking chemistry not history where did this greek prefix business come from we're going to use greek prefixes to denote the number of each atom present and these greek prefixes i've got these rules and the greek prefixes typed for you on the next slide so if you can't read my sloppy handwriting chillax you'll see them in a second but these greek prefixes are as follows the prefix mono equals one you kissed the one wrong person and you get mono die is two do not confuse die with bi bi means the presence of a hydrogen ion die means to then try everybody's had a tricycle tricycle i want to ride my tricycle right tricycle three three wheels tricycle all right tetra is four everybody's played the game of four-sided objects tetris on their cell phone penta everybody knows a pentagon is five sides just like everybody knows a hexagon is six sides hepta is seven don't have a good one for that octa is eight octopus nana and nine both begin with the letter n and then deca and ten ten years in a decade see boom you've memorized those greek prefixes right here right now no problem so if we look at our molecule here we have carbon and oxygen so we have carbon oxide now we need to denote the number of each we have one carbon we would use the prefix mono except carbon's the first element by convention you never use the prefix mono on the first element you do however have to use it on the second element so just to name another compound real quickly this compound just co would be carbon and then you have oxygen become oxide and you have one carbon you admit the prefix mono but you have one oxygen so you include the prefix mono for oxygen so this would be carbon monoxide over here however in our original example in our original example we have carbon and we have one so we emit the prefix mono we have oxygen and we have two of them so we use the prefix dye so it's carbon dioxide chemistry is easy life is hard right i had to work hard to come up with all those rules just to make this sound impressive so that you pay me for my services all right let's take a look at another example okay here are the rules for naming a covalent compound and this is part of that flow chart that you saw big if you've if you've been doing my nomenclature series with me my nomenclature trilogy the best trilogy since star wars um if you've been working through your videos for me this is part of that larger chart we have an ionic compound when we say is the first element of metal or ammonia no that means we have a covalent compound or two non-metals we write the name of the first element write the name of the second element with the suffix ide and we use the greek prefixes to denote the number of each so let's do another example here we have that staring at us on an exam and right off the bat i throw you a little bit of a curveball because i have boron and boron's a metalloid generally you treat metalloids or at least i always treat metalloids um as covalent compounds by default there are examples of colo of metalloids forming ionic compounds however though so watch that one but in this scenario if we subtracted the electronegativity differences we'd find it's a covalent compound so we write the name of the first element whoops that's not going to show up is it we write the name of the first element write the name of the second element with the suffix id so chlorine becomes chloride use prefixes to denote the number of each we have two borons so diboron we have four chlorines so tetra so it would be diboron tetrachloride one good example deserves another is what i've always said oh really was that a good example you threw a metalloid at us violating the first rule you're trying to yeah yeah yeah yeah everybody's a critic let's take a look at one of our nitrogen containing compounds all right we have two non-metals so we have a covalent compound so we write the name of the first element nitrogen we write the name of the second element with the suffix ide so oxygen becomes oxide we use our greek prefixes we have two nitrogens so it's dinitrogen we have five oxygen so well i'm just gonna make a mess of it there so it's di nitrogen penta oxide chemistry is easy life is hard yes just to make sure this horse is dead let's do a couple more examples all right we've got this one we have two nonmetals carbon and fluorine so we write the name of the first element carbon we write the name of the second element fluorine fluorine is going to become fluoride we have four fluorine so it's tetra carbon tetrafluoride two non-metals phosphorus and bromine we write the name of the first element phosphorus we write the name of the second element the suffix ide denote the number of each so it's phosphorus penta bromide quick comment something fun to talk about at parties why is it that we admit the prefix mono on the first element but never on the second here's the reason if i want to talk about this compound right here i call it carbon monoxide but if i want to talk about all the compounds that contain carbon and oxygen all of them in the entire universe so i want to talk about all the compounds that can be made from only carbon and oxygen i refer to them as carbon oxides so that winds up being a sort of family name if you would whereas this refers to just the individual compound this refers to the family of compounds you see this a lot you see the family names used a lot with sulfur and nitrogen compounds acid rains died away is a big hot environmental issue i don't see people protesting in the streets anymore like they used to but socks and nox were major contributors to acid rain right all these compounds contain only nitrogen and oxygens so their nitrogen oxides all of these guys however if i want to talk about just that compound right there that compound is nitrogen monoxide so that's the reason we have to include that mono on that second element there just in case you were curious about that and i knew that you were all right let's keep going here we haven't gone in reverse know what we also haven't done i haven't told you yet to watch arrow on the cw you should be watching arrow it's a really awesome show why don't you write down the word arrow everybody should write down the word arrow i hope you're writing down the word arrow all right let's go from the name to the formula going from the name to the formula is so ridiculously easy for these guys you see that looking at you on an exam you see a greek prefix right away that makes you happy because it lets you know you have a covalent compound you also see you have two non-metals so you know you have a covalent compound so you write the elemental symbol for each and then you use the prefix to tell you the number die so two nitrogens mono so one oxygen boom you're done drop the mic all right sulfur hexafluoride sulfur hexafluoride we have sulfur we have fluoride or fluorine we have six so it's hexa nothing there so it must be one so boom we're done in fun no way i'm stopping now tetraphosphorus and watch my spelling of phosphorus i did actually live overseas for a while and i lapsed into the queen's spelling ah good i'm on the right side of the pond at the moment all right tetraphosphorus trisulfide tetraphosphorus trisulfide so we've got phosphorus we have sulfur we have tetris so we've got four phosphorus we have three sulfides so p4s3 chemistry is easy life is hard there's nothing i can do to make this difficult all right that's it for naming simple binary covalent compounds thank you for joining me and see you here next time same bat time saying that channel