Octahedral??

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Frederick Keith_4C
Posts: 65
Joined: Thu Sep 26, 2019 12:19 am

Octahedral??

Postby Frederick Keith_4C » Sun Nov 17, 2019 1:33 pm

I understand that linear electron arrangements have 2 atomic orbitals, trigonal planars have 3, tetrahedrals have 4, and trigonal biyramidals have 5. But why do octahedrals only have 6? Doesn't octa- mean 8? So how come it isn't called a hexahedral or something?
I am definitely missing something...

Naji Sarsam 1F
Posts: 104
Joined: Sat Aug 17, 2019 12:18 am

Re: Octahedral??

Postby Naji Sarsam 1F » Sun Nov 17, 2019 1:36 pm

The name octahedral refers to the shape that a six atom molecule makes. This is because the term is a geometric one, as octahedral refers to the geometric shape hacing 8 faces, thus octa. However, the shape only has 6 vertices, which in a molecule is the 6 atoms.

Aiden Metzner 2C
Posts: 104
Joined: Wed Sep 18, 2019 12:21 am

Re: Octahedral??

Postby Aiden Metzner 2C » Sun Nov 17, 2019 1:37 pm

I think it is because of the fact that it is a 3-D shape. So if it were in 2D it would be hexagonal, but due to the fact that it has molecules all of bond angle 90 degrees on the xyz plane it is an octahedral. Lavelle explained something about how the shape when drawn in geometric patterns relates to an octahedral.

zfinn
Posts: 106
Joined: Fri Aug 30, 2019 12:16 am

Re: Octahedral??

Postby zfinn » Sun Nov 17, 2019 1:37 pm

It's octahedral because the shape of the whole molecule looks like an octahedron (8 faces). It's basically another way to describe the bipyramidal shape, which is two 4-faced pyramids put together, creating an 8 faced shape.

Naji Sarsam 1F
Posts: 104
Joined: Sat Aug 17, 2019 12:18 am

Re: Octahedral??

Postby Naji Sarsam 1F » Sun Nov 17, 2019 1:38 pm

This is the same as tetrahedrals. They are not called tetrahedrals because the molecule has four atoms, rather it is the mathematical term for the shape with 4 equal faces. It just happens that 4 atoms arrange themselves into the vertices of the tetrahedral


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