In this video, we're going to talk about how to name covalent molecular compounds. Now, the first thing you need to be able to do is you need to be able to distinguish a molecular compound from an ionic compound because the rules for naming these compounds are different. For example, MgCl2 compared to Scl2.
MgCl2 is called magnesium. chloride whereas SCL2 is simply called sulfur dichloride notice the difference SCL2 is known as a molecular compound MGCL2 is known as an ionic compound So for ionic compounds, you don't use prefixes like mono, di, tri, tetra, and things like that. It's just not necessary.
But for molecular compounds, you do need to use them. Now how do you distinguish an ionic compound from a molecular compound? Typically, an ionic compound contains ions, it has charges.
But 99% of the time, you can identify a metal inside it. It's usually composed of a metal and a nonmetal. An exception might be like ammonium nitrate. If you see ammonium, just know that it's ionic.
But for the 99% of the other times, it's going to be composed of a metal and a nonmetal. Magnesium is a metal, chlorine is a nonmetal. That makes it an ionic compound.
Typically, when you have two nonmetals combined, you're going to have a molecular compound. Sulfur and chlorine are both nonmetals. And in this video, we're going to focus on... naming molecular compounds. Now before we begin, we need to go over the prefixes and the values that they represent.
So if you see the word mono, mono represents one, di represents two, tri represents three, tetra is associated with the number four, penta represents five, Hexa is equivalent to 6, hepta is 7, octa is 8, nana is 9, and deca represents 10. So make sure you know these prefixes. You have to commit them to memory if you want to do well on your next test. So let's work on some examples. Let's say if we want to name CO and CO2. Both of these are molecular compounds.
Now, the first element, if there's a coefficient, I mean not a coefficient, but a subscript of 1, which means if you don't see a number, it's assumed to be 1. If the first element has a subscript of 1, don't use the prefix mono. You can use the prefix mono for the second element, but not for the first one. So this is called carbon.
monoxide because there's one oxygen. You don't want to say monocarbon monoxide. It doesn't work that way.
The second example is known as carbon dioxide because there are two oxygens. How can we name these two compounds? Feel free to pause the video and work on that example.
So starting with NO2, We're not going to say mononitrogen, which is going to say the name of the first element, nitrogen, and there's two oxygens, so nitrogen dioxide. For the second example, there's two nitrogens, so we've got to specify it using one of the prefixes. So two represents di, so this is going to be called dinitrogen, and five is associated with the word penta, so we're going to say pentoxide. Notice that the second element ends with the suffix ide.
Now at this point, I'm going to give you a ton of examples so you can master the topic of naming covalent molecular compounds. So go ahead and try these two, NO and N2O3. So NO is not mononitrogen, but simply nitrogen.
monoxide since we have one oxygen as the second element. So never use the prefix mono for the first element. Now the second example, we have two nitrogen atoms so we're going to use the prefix di- so it's going to be di-nitrogen and since we have three, three represents tri- so three oxygen atoms will be trioxide. So as you can see, if you know the ten prefixes that we went over earlier, It's going to be a piece of cake to name these things. It's not too difficult.
Here's some more examples that you could try. PCL3, PCL5, CBR4, and OF2. So feel free to pause the video and take a shot at these. So let's start with PCL3. So this is simply going to be phosphorus.
trichloride since we have three chlorine atoms. So what about PCL5? Now 5 is associated with the prefix penta so this is going to be phosphorus pentachloride.
You don't want to say pentachlorine, make sure you use the suffix "-ide". What about CBR4? 4 is associated with the prefix tetra. So this is called carbon tetrabromide. Now what about our last example, OF2.
This is called oxygen difluoride. Notice that the more electronegative element has the ending IDE. Electronegativity increases towards fluorine, and so fluorine is more electronegative than oxygen. That's why fluorine has the IDE ending.
In PCl3, chlorine is closer to fluorine than phosphorus, so chlorine is more electronegative. As you travel towards the right and up across the periodic table, the electronegativity of the elements increases. So the element that is more electronegative will have the IDE ending. So here are a few more examples that you can try.
SiF4, SiF6, If7, and P4O10. So take another minute to work on those problems. So Si stands for silicon, and F is fluorine, so we're going to say fluoride.
And because there are four fluorine atoms in SiF4, we're going to use the prefix tetra. So it's going to be called tetrafluoride. So that's the name for the first example. Now what about the next one? SF6.
S stands for sulfur. And we have six fluorine atoms. Six is associated with the word hexa. So this is going to be called sulfur.
hexafluoride. Now what about IF7? I is the symbol for iodine and 7 is associated with the word heptah so this is going to be called iodine heptafluoride. Now finally what about P4O10? How can we name that?
So we have four phosphorus atoms, so we're going to use the prefix tetra. So this is going to be called tetraphosphorus. And 10 is associated with what prefix, if you remember?
10 is deca, so we're going to say decoxide. It's going to sound weird if you have two vowels, decaoxide. So typically the A is omitted. So now you know how to name... covalent molecular compounds.
So look out for my next video on writing the formulas of molecular compounds. So if you check my chemistry video playlist you should be able to find it or you can access all of my playlists if you go to my channel. So if you need help with physics, chemistry, algebra, trig, calculus, you can check out my channel for those videos.
So thanks for watching and have a good day.