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bond angles

Posted: Thu Nov 15, 2018 11:05 am
by Roni Touboul
how do we figure out what the bond angles are?

Re: bond angles

Posted: Thu Nov 15, 2018 11:14 am
by Nicole Lee 4E
You arrange the bonding pairs and lone pairs around the central atom in a way that minimizes electron pair repulsion. For molecules where there is no lone pair around the central atom, the bond angles are 180 degrees for molecules with 2 bonding pairs around the central atom, 120 degrees for 3 bonding pairs, 109.5 degrees for 4 bonding pairs, 120/90/180 degrees for 5 bonding pairs, and 90 degrees for 6 bonding pairs.

Re: bond angles

Posted: Thu Nov 15, 2018 11:20 am
by Sarah Jeong 4F
You could think logically for some of them, for example how a triangular planar is equal angles, and therefore is 360/3=120 degrees. For some, it's just pure memorization. This is a very useful chart I found!
image.png

Re: bond angles

Posted: Mon Dec 03, 2018 11:51 pm
by taywebb
Does anyone know if there are ways to figure out if the bond angles are not the standard 90, 109.5, 120, 180 and how we would denote on the final if they were more or less than that?

Re: bond angles

Posted: Mon Dec 03, 2018 11:54 pm
by Sydney Aurelio_Dis4B
@taywebb Yes if there is a lone pair on the central atom it would make the bond angles slightly less than the standard. This is because the lone pairs repel the other atoms away from itself making their bond angles slightly smaller

Re: bond angles

Posted: Mon Dec 03, 2018 11:59 pm
by jguiman4H
This chart also sums up the point made above. The presence of lone pairs typically alters the bond angles to less/greater than expected, except in the two cases seen (steric number 5, linear shape and steric number 6, square planar shape) as these electrons can be placed anywhere on the axis, so they repel equally.

https://web.chem.ucsb.edu/~devries/chem1C/handouts/Molecular%20Geometry%20chart.pdf