To write a formula that stands for the exact compound you have in mind, you often must write the structural formula instead of the molecular formula. Structural formula: Add the bonding pattern The structural formula shows the elements in the compound, the exact number of each atom in the compound, and the bonding pattern for the compound. Structural Formula. A structural formula shows the chemical bonds. This is important information because two molecules may have shared the same number and type of atoms, yet be isomers of each other. For example, ethanol (grain alcohol people can drink) and dimethyl ether (a toxic compound) share the same molecular and empirical formulas.
What I want to do inthis video is think about the different ways torepresent a molecule. So the most obvious way is its name. So, for example, you could be referring to a molecule of benzene. But just the word 'benzene'tells you very little about what actuallymakes up this molecule. And there's other namingconventions that do give more information, but you might say, well, I actually want to know more about the actual particularelements that make it up.
Well, that might be, in that case, it might be useful to moveup to the empirical formula. Empirical, empirical. Empirical formula.
And you might be thinking, what does empirical mean? In general, the word 'empirical'is referring to something that comes from observationor comes through experiments. If you could say hey, youknow, I from empirical evidence I now believe this, thismeans that you saw data.
This means that you havesome observations that make you think this new thing. The reason why we call whatI'm about to write down the empirical formula, isbecause early chemists, they can't look, theyweren't able to look at just one molecule, butthey could at least come up with, they could observethe ratios of the different elements that they had in a molecule. So an empirical formula gives you a ratio of the elements in the molecule. So an empirical formula for benzene is. One carbon for every, for every hydrogen.
Now you might say, OK, that's nice, I now know that if I'mdealing with benzene I have one carbon for every hydrogen or one hydrogen for every carbon, but what does, how many ofeach of these do you actually have in a benzene molecule? To answer that question,that's when you would want to go to the molecular formula. Molecular formula. And the molecular formulafor benzene, which is now going to give us more information than the empirical formula,tells us that each benzene molecule has six hydrogens, and, sorry, six carbons and six, (laughs) I'm really having trouble today, six hydrogens, (laughs) six carbons, and, six hydrogens. Now, the ratio is stillone to one, you get that right over here, it's very easy to go from a molecular formula toan empirical formula. You essentially are losing information.
You're just saying the ratio, OK, look, it's a ratio of six to six, which is the same thing as one to one. If we wanted to, wecould write this as C one H one just like that toshow us that the ratio for every carbon we have a hydrogen. And we see that that's actuallythe case in one molecule, for every six carbonsyou have six hydrogens, which is still a one to one ratio. That may not satisfy you, you might say, well, OK, but how are these six carbons and six hydrogens actually structured?
I want more information. And for that, you would wanna go to a structural formula. Structural formula, which will actuallygive you the structure, or start to give you thestructure of a benzene molecule. A benzene molecule would be drawn like. So you would have sixcarbons in a hexagon.
So one, going to write this way, one, two, three, four, five, six carbons in a hexagon just like that. And then you have adouble bond, every other of these bonds on thehexagon is a double bond. Each of these carbons arealso attached to a hydrogen, also bonded to a hydrogen.
Each of these lines that I'm drawing, this is a bond, it's a covalent bond, we go into much more depthin other videos on that, but it's a sharing ofelectrons, and that's what keeps these carbons near eachother and what keeps the hydrogens kind of tied to each, or, the hydrogens tied to thecarbons and the carbons tied to the hydrogens. So let me draw it just like this. And this is only onevariant of a structural, it's hard to see this one I just drew, so let me see if I can do a little bit.
Oh, that's about as good,hopefully you see there's a hydrogen there, and there'sa hydrogen right over there. This is one variant ofa structural formula, some structural formulaswill actually give you some 3D information, willtell you whether a molecule is kind of popping in or out of the page. Others might not be as explicit, once you go into organic chemistry chains of carbons are justdone, they're just. You might see somethinglike this for benzene, where the carbons are implicitas the vertex of each, there's an implicit carbonat each of these vertices, and then you say, OK, carbon's gotta have, not gotta, but it'stypically going to have four bonds in its stable state,I only see one, two, three. Well, if it's not drawn,then it must be a hydrogen. That's actually the convention that people use in organic chemistry.
So there's multiple waysto do a structural formula, but this is a very typicalone right over here. As you see, I'm just getting more and more and more informationas I go from empirical to molecular to structural formula. Now, I want to make clear, that empirical formulas and molecular formulasaren't always different if the ratios are actually, also show the actual number of each of those elements that you have in a molecule.
A good example of that would be water. Let me do water. Let me do this in adifferent color that I, well, I've pretty muchalready used every color. So water we all know,for every two hydrogens, for every two hydrogens, and since I already decided to useblue for hydrogen let me use blue again for hydrogen, for every two hydrogensyou have an oxygen. You have an oxygen.
It just so happens to be,what I just wrote down I kind of thought of interms of empirical formula, in terms of ratios, butthat's actually the case. A molecule of hydrogen,sorry, a molecule of water has exactly two hydrogens and, and one oxygen. If you want to see the structural formula, you're probably familiar with it or you might be familiar with it. Each of those oxygens in a water molecule are bonded to two hydrogens, are bonded to two hydrogens. So hopefully this at least begins to appreciate different ways of referring to or representing a molecule.
The chemical formula for alcohol that you drink is C6O2Na4 OK,this answer is completely false. First and foremost, for anyorganic compound to be classified as an 'alcohol' it has to have an'-OH' functional group. This C6O2Na4 answer has no Hydrogen atall!?? The alcohol you drink in alcoholic beverages is ETHYLALCOHOL also known as ETHANOL.
The chemical formula forethanol is most commonly written as CH3CH2OH (or in thecondensed empirical formula as C2H5OH or simply C2H6O). If you lookup ethyl alcohol on wikipedia you can actually see figures of theactual molecule. The difference between ethyl alcohol and methylalcohol (CH3OH) is the extra methylene group (CH2).
Methyl Alcoholis highly poisonous and can be fatal. However, the immediatetreatment for methanol poisoning is to consume mass quantities ofethanol very quickly since the body used the same metabolicpathways to break them both down. (Flood the pathway with ethanolwhich the body can break down). So every time you get wasted, justremember, you're protecting yourself from methanol poisoning!