How do we determine bond angles?

[EvaLi_3J]

For example, in 2E problem 5, how do we know what is the angle for ClO2+ ?

[Ronak Naik]

You have to predict its shape first using the rules we learned in the lecture. Then, you will know the bond angles. If the molecule is linear, then the angles will be 180 degrees. Trigonal planar - 120 degrees. Tetrahedral - 109.5 degrees.

[William Francis 2E]

This question does not ask for an exact bond angle to be given for ClO2+. I think it's asking more generally for the shape of the molecule. Since the central chlorine atom has one lone pair and is bonded to two oxygen atoms, we know that the molecule will have a bent, trigonal planar shape with an O-Cl-O bond angle less than 120 degrees since the repulsion between lone pairs and bonds is greater than that between bonds.

[htatshwe_3L]

If you can predict the shape of the molecule using VSEPR you can tell what the bond angles are, so in the case of ClO2+ it would be bent, as it has 2 things bonding to it and one electron pair.

[Rory Simpson 2F]

You can generally predict the bond angle based on the VSEPR molecular structure (eg a tetrahedral molecule would have bond angles of 109.5 degrees). If a central atom has lone pairs, using VSEPR you can approximate the bond angle just knowing that the lone pair-atom repulsions are greater than atom-atom repulsions, but it would be hard to get an exact number for atoms with lone pairs because it varies for difference molecules with the same molecular shape (as Dr. Lavelle said in lecture).