(Polar molecules, Non-polar molecules, etc.)
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Can someone explain how we knows what the bond angles are? I'm still confused about how we know that, or like how we know that an angle is less than some other angle(for example when they say that an angle is <120, how do they reach that conclusion)?
Bond angles were covered in lecture and can also be found in the textbook. Bond angles are affected by repulsion between electrons, with stronger repulsions between lone pair and lone pair electrons and weaker repulsions between bonded pair and bonded pair electrons.
Bond angles can be generalized and predicted based on shape, but will slightly differ based on certain atoms. Also, lone pairs contain additional force which pushes bonding electron pairs closer together, making bond angles smaller. I do not think we have to be able to determine bond angles, but we should be aware what could make them smaller / be able to estimate based on shape.
I think we can predict the bond angles using the VSEPR theory, so for example how long-pairs repel each other more than lone-pairs repel a bonding pair. So if we have a lone-pair of electrons on the central atom we will know that the other atoms bonded to the central atom will be pushed down and the bond angles will change accordingly.
Hope it helps!
Hope it helps!
We can predict the bond angles using VSPR, which is based on electron electron repulsion between lone pair electrons and bonding pair electrons. In terms of finding the exact value of the bond angles, this may not be always known, as many times the angles are described as being "less than" a certain amount, in which we do not need to know the exact angle.
Guzman_1J wrote:Can someone explain how we knows what the bond angles are? I'm still confused about how we know that, or like how we know that an angle is less than some other angle(for example when they say that an angle is <120, how do they reach that conclusion)?
an angle may be smaller than 120 because there is a lone pair of electrons that will "push" the bonded electrons down and therefore, decrease the bond angles. the unpaired electrons have a negative charge that is repelling the electrons in the bonded pair, moving them and impacting the bond angle.Also remember lone pair electrons hold a larger volume in which that space has a negative charge. This is another factor that decreases bond angle
Professor Lavelle referenced in his lecture that repulsion strength goes in this order (LP-LP, LP-atom, atom-atom) thus the lone pairs will exert a bigger repulsive force on the other atoms making the other atoms get closer together (becomes less than 120 degrees or 109.5 what have you) so the LP can stay father apart.
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