Order of atoms about the central atom

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Katherine Fitzgerald 1A
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Joined: Fri Sep 29, 2017 7:05 am

Order of atoms about the central atom

Postby Katherine Fitzgerald 1A » Tue Jul 23, 2019 8:02 pm

I'm not clear on the guidelines for determining the arrangement of atoms of different elements around a central element. For instance, in E25(a), we are asked to draw the lewis structure and determine the shape of CH2Cl2. How do we know whether the H or Cl is the one at the top of the tetrahedron, or on the base? In the lewis structure, should the H and H be next to each other, or should H and Cl alternate around the central atom? Or does it not matter?

Any other related rules that I should be aware of?

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Re: Order of atoms about the central atom

Postby Chem_Mod » Tue Jul 23, 2019 11:53 pm

The structure of CH2Cl2 is tetrahedral. All the non-central atoms will be approximately 109.5 degrees away from each other. Lewis structures show a 2D image but the real 3D image is a tetrahedral so no matter where you draw the chlorine atoms, they will technically always be next to each other. As long as you understand that the 3D image is tetrahedral, the arrangement of the atoms around the carbon atom is not too important as long as they are all single bonded to the central carbon atom.

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