Give the ideal bond angle for BrO3- ion?
I know this has trigonal bipyramidal geometry and therefore the bond angle is < 109.5. Is there a way to determine a more specific bond angle?
If I tell you it is 107.4 degrees, you will ask me why, so I wont tell you.
Hmmm. The "ideal" bond angle is 109.5 The "real" bond angle is what I gave you.
I believe the electronic geometry is tetrahedral and the molecular geometry is trigonal pyramidal and not trigonal bipyramidal. I don't know of any way to predict the exact bond angles; usually it's the other way around. That is usually we know the angle from measurements and we look for reasons to support that measurement.
Yes, there is a way to determine a more specific bond angle for the BrO3- ion. To do this, we can use the concept of VSEPR (Valence Shell Electron Pair Repulsion) theory. VSEPR theory predicts the shape of molecules and ions based on the repulsion between electron pairs around the central atom.
In the case of the BrO3- ion, the central atom is the bromine (Br) atom, and it is surrounded by three oxygen (O) atoms. The electron pair geometry for BrO3- is trigonal bipyramidal, as you correctly mentioned.
To find the bond angle, we need to consider the three types of electron pairs around the central atom:
1. Bonding pairs - These are the electron pairs involved in forming bonds with other atoms. In the case of BrO3-, there are three bonding pairs between the bromine atom and the three oxygen atoms.
2. Lone pairs - These are the electron pairs that do not participate in bonding and are present only on the central atom. In the case of BrO3-, there are two lone pairs on the bromine atom.
Now, let's determine the bond angle by looking at the repulsion between the electron pairs:
1. The bonding pairs and the lone pairs repel each other.
2. The lone pairs repel more strongly than the bonding pairs because they are localized closer to the central atom.
Due to this repulsion, the two lone pairs on the bromine atom will push the three bonding pairs away from them, resulting in a distortion of the ideal trigonal bipyramidal geometry.
As a result, the bond angle in the BrO3- ion is actually less than the ideal trigonal bipyramidal angle of 109.5 degrees. Considering the lone pair repulsion, the bond angle is approximately 105 degrees.
Therefore, the more specific bond angle for the BrO3- ion is around 105 degrees.