Smallest Bond Angle

[Ruth Rosales 3D]

How do we come to determine the smallest bond angle?
Based on one of the questions from Sapling week 8.

Are we meant to memorize the angles for each shape? Because that is how I've been answering these questions.

How do you guys usually approach questions like these?

[Christine Ma 3L]

For these types of questions I would draw out the Lewis structure (if not already given) to see how many bonding and lone pairs there are around the atom in question. Then I would use VSEPR to find the shape which then gives the bond angles. Hope this helps!

[Algernon Jackson 2l]

Use the VSEPR theory, there are also charts on google images; just search up molecular geometry.

[Marc Lubman 3B]

The smallest bond angle depends on the surroundings of a particular pair of bonds. Different types of regions of high electron density have different strengths of repulsion, and thus the bond angle will be smaller if a pair of bonds is surrounded by regions with particularly high repulsive strength, or a greater number of regions of high electron density. For example, take the comparison of the methane (CH4), boron trichloride (BCl3), and water (H2O) molecules. Both water and methane have 4 regions of high electron density whereas boron trichloride has 3, so boron trichloride has a greater bond angle than those two. Between water and methane, we must look at the types of regions of high electron density. In methane there are four covalent single bonds and in water there are two covalent single bonds and two lone electron pairs. Lone electron pairs are more repulsive than covalent bonds, so water will have a smaller bond angle than methane.

[Ellison Gonzales 1H]

If you’re talking about the smallest bond angle when comparing the angles within one structure, I see the smallest angle as being the one between two bonding pairs. Since there is more e- repulsion between a lone pair and a bonding pair, that will cause the other angles without lone pairs to be smaller.