shoutout e rintoul u living legend man is making moves out here coz of you, no understatement but you make chemistry a level so easy maybe even easier than btec science hahahhaha, large up E RINTOUL, jazakallah bruda, watch a roley coming thru ur post in due time!
You are seriously a life-saver. Why can't I have the same teacher with the same teaching qualities? :( Best Chemistry teacher in this Universe, seriously! Thank you so much for your amazing videos! I don't know how much I've thanked you xD Probably a hundred. :)
you make chemistry a level so easy to understand, you're better than both of my chemistry teachers and you move at such an understandable pace, it's coz of you if I get an A in chemistry thank you so much
These videos are life savers. You're excellent at explaining everything we need to know. Don't ever stop making these videos I beg if you. Without you I have no hope of at least B in chemistry. Thank you. You're way better than probably all of the other chemistry A Level teachers out there. You go over exam style questions which is really important. And the way you explain the theory side of the spec us brilliant. 👌
This video is fantastic, I watched it just to revise over a few topics I didn't quite grasp in lesson and the subject of shapes of molecules finally makes complete sense now! :D
A tip: for figuring out how to draw it E.g NH3 1. Number of electrons on outer shell of centre atom (N has 5) 2. Number of bonded pairs (3 A’s it’s bonded to 3H) 3. 5-3=2 4. 2/2=1 5. So you have 3 boned pairs and one lone pair
sir you are amazing thank you for all your great work and your time ,you really are saving my life, my book doesn't isn't providing me with all these details while the teacher is explaining them in class and I was completely lost until I watched this video today. thank you very much really God bless you . may God also shower you with happiness where ever you go! imma cry your videos are just so amazing!!! Thank youu! you are very kind for uploading all these helpful videos.
If you still need help with your A Levels, check out Alt Academy, we have a LOAD of resources that you can use for your exam prep. Video Lessons, Flash Cards, Handwritten solved past papers with explanations, Live Yearly Past Paper solutions, revision guides, 24/7 academic support and SO MANY more things. You'll ace your exams!
chemistry alevel is killing me and you've saved my life! thank you so much! only thing is, please make your cursor more visible because sometimes I cant see what you're pointing to
Thanks for this great video, it kind of makes sense now :) So are all the shapes and names outlined in this video all we need to know? I recall my teacher saying things like "see saw" and other confusing names, is there a list of all the names for the shapes we need to know for the exam? Thanks in advance.
Thank you so much for the videos,,,,they are too good !!! Would you be able to do a video on how to draw lewis dot structures for complicated molecules like HNO3....and how to calculate formal charges...
Hilfe! Hi! What do you mean by calculating formal charges...? To be honest, there's little need for lewis dot structures at all at AS, and certainly not for annoying molecules! Let me know if there's something I can help you with though!
I know this is a long time after you uploaded this (!) but I'm just wondering for the very last bit, how you knew flourine was only bringing 1 electron? When I tried to work it out I said 7 because that's how many are in its outer shell, then I ended up with 16 bonding pairs!! (which is obviously wrong lol)
If you still need help with your A Levels, check out Alt Academy, we have a LOAD of resources that you can use for your exam prep. Video Lessons, Flash Cards, Handwritten solved past papers with explanations, Live Yearly Past Paper solutions, revision guides, 24/7 academic support and SO MANY more things. You'll ace your exams!
Thank you soo much for you're helpful video. But my question is what if there is no central atom. For instance CH3OH where C and O are in the middle and H are around them. How do we do that?
When working out the shape, how do you know if the bonds are double or not? Like obviously C02 has double bonds but if you didn't know this wouldn't you be inclined to draw it as a trigonal planar with one lone pair?
How do you know that CH4 is 3D and so the bonds aren't in the same plane? Couldn't you just draw the bonds as a square - how do you know not to do this? Thanks!
I'm just a little confused about this. So as you said 4 bonding pairs= a tetrahedral shape, for example CH4, 109.5 degrees. However with Ammonia, there are only 3 bp and 1 lp so why is it not based off of 120 degrees
i am using your video playlists to prepare and recap for my upcoming cie exam in 20 days or so! hopefully there's not much difference in AQA and CIE chemistry :)
Hi there 🙂 Hope your revision is going well. I have a free AS revision course playlist with resources here: ru-vid.com/group/PLaD6fcqFKTWjj4-QnOs4kQJQcym1EHsRo Best of luck with your exams.👍
Yeah, you're spot on. And as I said in the video, the new bond angle is calculated based on a tetrahedral shape that has had the bonding pairs replaced with lone pairs, each one causing 2.5 degrees of constriction.
GTAV FRANKLIN Strong name. However I think I prefer Trevor. As for your question, kind of yes and kind of no. It's best to think of the shape as it is... the central atom with the 3 bonded atoms e.g. NH3. You are correct though that the bonding pair of electrons has just been replaced with a lone pair and that's particularly helpful when it comes to calculating the bond angle. Normally a tetrahedral molecule would have a bond angle of 109.5 but with the bonding pair replaced by a lone pair, there is more constriction on the remaining bonding pairs and so they get squished down by 2.5 degrees, resulting in that delightful 107 degree bond angle! That helped?
At 17:33 why does the F4 only account for 4 electrons? Fluorine is in group 7 so why doesn't it donate 7x4 electrons (ie 28) I understand that I am wrong in thinking this but I would like an explanation as to why the fluorine is only accounted for 1 electron. Thanks
+Jason Bourne I think he means how many other bonds are there going to be, rather than electrons. So when he did it for H3 he did 3x1, so for F4 it was just 4x1.
+Jason Bourne I see what you are saying, but in a covalent bond, fluorine never shares 7 electrons. Instead it shares one and has one shared with it as a result, giving it that lovely full outer shell. In this case, each one of the four fluorine atoms shares one, hence four! That help?
On the Jun 13 paper, a Q asked to draw the shape of the TlCl2 ion. I worked out there was 2 bond pairs and 2 lone pairs. Am I right. If im wrong can u go through it from step 1-5??
DS_2808 That is wrong, but I can certainly show you what to do! They've used thallium to make it all seem much more difficult than it is. The fact that they talk about aluminium is a give-away - thallium has 3 electrons in its outer-shell, just like aluminium (you can also see this from them both being in the same group - group 3). So the thallium has 3 outer electrons. Following my method, each chlorine brings one. This brings our total now to 5. A positive charge means that one electron has been lost, bringing our total to 4. Dividing by 2 give 2 pairs. There are 2 chlorines bonded, each requiring a pair of electrons. Therefore the 2 pairs anre bonding pairs with no lone pairs present. This means that the shape is just linear. Does that help at all?
EVERYONE according to the JAN2010 CHEM1 MS bent-linear is a contradiction so it would not be credited. They gave you credit for the following: 1) Bent 2)V shape (as sir suggested in the video) 3) Non-linear 3) triangular 4) Angular This was for the ClF2+ ion but I think its the same principle for water as well ( if not please correct me!)
E Rintoul Hir sir i am confused about q1bi and bii on : filestore.aqa.org.uk/subjects/AQA-CHEM1-QP-JAN12.PDF ok so i got the structure correct for both but for the bond angle in bi) i put 104.5 as there are 2 lone pairs, however the MS says 120. I understand that the shape is trigonal planar, but since lone pairs have greater repulsion shouldn't the bond angles be lower than 120? thanks
commando1776 I can see what you're saying. You are correct that the lone pairs repel more. And this forces them to opposite sides of the central atom. The remaining atoms form a trigonal planar shape, hence the 120 degrees. Does that make sense?
E Rintoul ok so basically if the molecule still has a trigonal planar shape the bond angles will be 120 regardless whether or not the central atom has lone pairs ? 1 more question, will all molecules with 4 bonds and 2 lone pairs have a square planar shape with bond angles of 90? thanks!
commando1776 Yes and no. If it had the 3 bonding pairs but one lone-pair, it would be a trigonal pyramid. By having the 2 lone-pairs, their repulsion means that they push as far away as possible, squeezing the others into the central plane. And yeah, 90 degrees in that case!
Hi. I've tried using the method you explained for working out the shape of SO3 but I got lost and I can't work it out. Would you mind explaining this to me? Thanks.
hi eliot, you know at 12:58, why is it 104.5 degrees, if conventional linear has 180 degrees, -5 degrees for 2 lone pairs = 175 degrees? this is so confusing
I am still so lost, I’ve tried to follow the steps for BCl3 but it makes no sense. The central atom provides 3, the bonding atoms provide a total of 21, giving 24. 24/2 = 12 electron pairs? But the molecule only has 3 bonding pairs, so where does the 12 fit in?
Hi, I know this video is a while ago but I was just wondering how you would know there are lone pairs involved when drawing shapes of molecules? Thanks
Look at the number of valent electrons (electrons in the outer shell) and see how many of them aren't bonded to other atoms. For example, in H2O, we have an oxygen atom that has 6 electrons in its outer shell, two of them are bonded covalently to two hydrogen atoms (6 - 2 = 4) so we are left with 4 electrons, which form two pairs. So in a H2O molecule, the oxygen has two lone pairs.
I am confused on how you incorporate the lone pairs in aswell... Is there a rule that concerns what shape something should be depending on how many lone pairs there are... Eg with BrF3 I could work out there were 3 bonding pairs and 2 lone pairs but cannot figure out how you would draw this?
riahlouise There are 2 ways to draw this; the first is as Reece has said, and the other is a twist on the trigonal planar shape. You need to think about the fact that all the pairs of electrons, lone or bonding, will repel one another. In this, the lone-pairs will repel more than the bonding pairs. I find it easiest to think of the lone-pairs shifting to be completely opposite, with the bonding pairs in the same plane in the middle of the molecule. In this case, the bond angle is 120 degrees. That helped at all?
Reece Johnson Yeah, good job. The other option is the lone-pairs being completely opposite to one another with the 3 bonding pairs in the middle in a trigonal planar set-up. This would give a bond angle of 120 degrees.
sir, What happens when your atoms have double bonds, don't we treat them as single bonds which will change the shape totally? Should we see whether the central atoms share double bonds before we start to do anything? thanks a lot! p.s i am having trouble doing SO3, it's a trigonal planar (3 bond pairs), but can you please tell me why?
Rangahatimuhmon I wouldn't worry about double bonds. Concentrate on single bonds (besides CO2) and make sure you have their shapes down. SO3 is a difficult one. I've seen conflicting points about it so I think it's best to ignore it!!
Rangahatimuhmon Sorry for not replying, RU-vid doesn't do a great job at making it easy to see replies! It's pretty safe to say that you'll be dealing with single bonds!
In a word, no! The names are a give-away to the shape - the trigonal pyramid is a triangle-based pyramid and the bipyramid is similar, but there are two pyramids! The best way to see this is to look at diagrams of molecules that exhibit these shapes. This link will show you ammonia (ts2.mm.bing.net/th?id=HN.608039276177525953&pid=15.1) and this will show you phosphorous pentachloride (upload.wikimedia.org/wikipedia/commons/thumb/c/c5/Phosphorus-pentachloride-3D-balls.png/540px-Phosphorus-pentachloride-3D-balls.png). The ammonia molecule has a trigonal pyramid shape (imagine joining the bottom three atoms together - you'd see a triangle). The phosphorous pentachloride has a trigonal bipyramid shape, though. If you look, you'll see that the top atom and the three in the middle make the same trigonal pyramid as before (ignore the very central atom in this case), then the bottom atom and the middle three atoms make another trigonal pyramid. Hence the BI in the name! Has that helped?
by knowing its hybridisation ! if it has 4 bonds it has sp3 hybridisation and angle would be 109.5 if it has 3 b.p then it has sp2 (120) if it has 2 b.p it has sp1 (180)
bit late lol but it's because in its valence shell Phosphorus has a s-subshell (2 e-), p-subshell (6 e-) and also a d-subshell (10 e-) meaning it actually has space for 18 electrons in its outer shell. It's called an expanded octet. Anyone feel free to correct if im wrong though
