Bond Angles [ENDORSED]

[Tamera Scott 1G]

For molecules with an octahedral shape, the bond angles can either be 90 or 180 degrees. How do you know which one to apply?

[Anushi Patel 1J]

That depends on the molecular geometry of the molecule. The shape of a molecule can be octahedral, but instead of all 6 of the groups bonded to the central atom being atoms, they can also be lone pairs. This changes the molecular geometry from octahedral, to square pyramid, to square planar, to t-shaped, to linear (as number of lone pairs increases). All the bond angles are 90 degrees except where there is a linear molecular geometry, and then there is a 180 degree angle.

[Ava Kjos 1D]

If you look at the diagram for an octahedral shape you can see that there are three atoms in the vertical direction that are in a straight line (or 180 degree angle). There's also 4 atoms located in the middle around this vertical line. These 4 atoms will repel each other and each form 90 degree angles to the atom next to it and 180 degrees from the atoms across. It will also form 90 degree angles to the top and bottom atoms of the vertical line. Once you establish that at a molecule is in an octahedral shape it might help to sketch it out so you can visualize whether it's a 90 degree angle or an 180 degree angle.