molecular shape

[Katherine Chhen 3I]

Based on the lewis structure, how are we able to determine the molecular shape since the lewis structure is only 2-D?

[Lindsey Chheng 1E]

Based on the lewis structure, how are we able to determine the molecular shape since the lewis structure is only 2-D?

To determine molecular shape, you have to take into account the steric number (# bonding regions + lone pairs) and the number of lone pairs. Determining the name of the molecular shape will basically depend on memorization skills.

[Shutong Hou_1F]

There are several general rules to help determine, and thus memorization is required.
To determine the molecular shape, both lone pair electrons and bonding pair electrons need to be considered; professor Lavelle hasn't discussed this in lecture yet.
However, to name the shape of the molecule, only positions of bond atoms, or bonding electron pairs need to be considered.
To name the molecular shape:
1) linear, 2 bonding pairs;
2) trigonal planar, 3 bonding pairs;
3) tetrahedral, 4 bonding pairs;
4) trigonal bipyramidal, 5 bonding pairs;
5) octahedral, 6 bonding pairs;

[simmoneokamoto3K]

There are several general rules to help determine, and thus memorization is required.
To determine the molecular shape, both lone pair electrons and bonding pair electrons need to be considered; professor Lavelle hasn't discussed this in lecture yet.
However, to name the shape of the molecule, only positions of bond atoms, or bonding electron pairs need to be considered.
To name the molecular shape:
1) linear, 2 bonding pairs;
2) trigonal planar, 3 bonding pairs;
3) tetrahedral, 4 bonding pairs;
4) trigonal bipyramidal, 5 bonding pairs;
5) octahedral, 6 bonding pairs;

As the person mentioned above, how its taught is that we should draw the lewis structure of the molecule initially (this includes meaning finding the resonance if necessary) and then seeing the configuration and as there are only five configurations, it should be fairly easy

[Ariel Davydov 1C]

There are also some really great Youtube videos that help you visualize the shapes of these molecules and understand them rather than depending on sole memorization. I highly recommend Tyler DeWitt's video on VSEPR. Hope this helps!

[Victoria Otuya 4F]

So first drawing the lewis structure can help, next is counting the bonds and lone pairs on the central atom, and then assigning the electron arrangement and lastly is identifying the shape considering only atoms.

[Katherine Chhen 3I]

Would we need to draw the Lewis structure with the correct formal charge in order to determine the molecular shape? Or can we just draw a general Lewis structure?

[kim 2I]

You should still draw the Lewis structure with the lowest formal charges since the number of bonds/lone pairs could change and therefore affect the molecular shape. However, you don't need to worry about resonance structures.

[Catherine Daye 1L]

You look at the regions of electron density. Count the number of bonds and lone electron pairs around the central atom. That shows you the VSEPR formula (AXE), and you can determine the molecular shape.