## 4.19 b

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

ClaireHW
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Joined: Fri Sep 29, 2017 7:07 am
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### 4.19 b

Hi could someone go over 4.19 b?
The question is:
Predict the bond angles at the central atom of (CH3)2Be

Thanks

(Claire Woolson Dis. 3J)

Amanda Hagen 1L
Posts: 26
Joined: Fri Sep 29, 2017 7:04 am

### Re: 4.19 b

The lewis structure is formatted H3-C-Be-C-H3 and each C atom has a tetrahedral molecular shape (AX3) with bond angles of 109.5 and Be has a linear molecular shape (AX2) with a bond angle of 180.

Posts: 20
Joined: Fri Sep 29, 2017 7:04 am

### Re: 4.19 b

As always, drawing the Lewis structure is the first step. When we draw the Lewis structure, Be is the central atom of the overall molecule, but the outer Cs are the respective central atoms for the right and left sides. We know that because Be does not ever attain a full octet, we should simply fill in the rest of the bonds until the carbons have full valence shells and all the electrons are used. Therefore, there are eight covalent bonds total, only two of which are on Be. And Be has no other lone pairs on it. Looking strictly at the bonds between the three central atoms, we know that the angle is 180 degrees and the shape is linear due to the fact that there are only two areas of electron density. However, we also need to consider the Cs as central atoms in themselves. Around each carbon there are four areas of electron density (all of which are covalent bonds), which means it has the bonding angles corresponding to the tetrahedral shape (angles at 109.5 degrees).

Isabelle Bautista 3H
Posts: 23
Joined: Fri Sep 29, 2017 7:06 am

### Re: 4.19 b

So does this mean in all cases such as (CH3)2Be or anything like that, we should also be considering the shape of the molecule with central atom 'C' in addition to the shape of the overall molecule? Basically anytime there is a compound inside a molecule, should we also name the shape of the specific compound?

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