Outlining Steps for Determining Shape

(Polar molecules, Non-polar molecules, etc.)

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Neha Divi 1K
Posts: 31
Joined: Fri Apr 06, 2018 11:02 am

Outlining Steps for Determining Shape

Postby Neha Divi 1K » Mon Jun 04, 2018 7:24 pm

Can someone outline the steps for determining the molecular and VSEPR shape? Like, how one should go about solving a problem when asked on an exam.

Zuri Smith 1A
Posts: 34
Joined: Fri Apr 06, 2018 11:05 am

Re: Outlining Steps for Determining Shape

Postby Zuri Smith 1A » Mon Jun 04, 2018 8:09 pm

This is the process I use, hope it helps! I used CH4 in exercise 4.73 as an example.

1. Count the # of valence electrons for each atom. For example, CH4: Carbon has 4 valence e-, H, has 4 x 1 e- = 8 e- total
2. Draw the correct Lewis structure -- check using the formal charge equation. For example, CH4 looks like one C surrounded by 4 H.
3. Determine the VSEPR by counting the lone pairs and atoms. The central atom is denoted by "A", the other non central atoms are "X" (subscript of X is the number of other atoms), the lone pairs on the central atom is "E". For ex: In CH4, each Hydrogen has 0 lone pairs and Carbon has 0 lone pairs. The only electrons are the bonds between each Hydrogen and the Carbon. Therefore, the VSEPR for CH4 would be AX4
4. Use the VSEPR notation to determine other characteristics of the molecule. These are things we should probably memorize. For ex, AX4 means the HCH bond angles are 109.5º. The molecule shape is tetrahedral and so is the orbital shape.


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