Bond Angles

[Samantha Chung 4I]

When we say that for example, the bond angle for a bent shaped molecule is less than 120 degrees, how much smaller is it exactly? Is there a way to determine? Or is it influenced by other factors as well?

[Esha Harwalkar 3F]

We don't have to know the exact bond angles, just that when a lone pair is added, the other atoms will repel from the lone pair a little more, causing distortions in the bond angles. For example, if we atoms in the plane and then add a lone pair of electrons ABOVE the plane, the atoms will tilt more downwards (away from the lone pair). In the bent shape, the VSEPR fomula is AX2E2, meaning there are 4 total regions of electron density, like in tetrahedral. In tetrahedral, the bond angles are 109.5 degrees, so when 2 of those regions are lone pairs, then the angles actually become a little less than 109.5 degrees, not 120.

[Gillian Ward 1F]

I don't think it is possible to find an exact figure for the bond angles that are, for instance, less than 120 or 109.5. There are only estimates or a range that it could be in.

[Nikki Bych 1I]

I believe that we just have to recognize that when there are lone pairs, the bond angles are depressed. i.e. 3 bonding pairs 1 lone pair, as long as you say bond angles are less than 109.5 degrees because of the lone pier you should be fine.

[Janelle Magaling 3L]

You would have to search up the exact degree of the angle since it is very particular. I believe for the test you would not need to know the exact angle, just that it is less than the typical given angle degree in an all atom structure.