Central atoms in Lewis Structure

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Hannah Morales 1D
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Joined: Fri Sep 29, 2017 7:06 am

Central atoms in Lewis Structure

Postby Hannah Morales 1D » Sat Nov 24, 2018 2:33 pm

I need a refresher on which atom should be the central atom and if there is any special cases? I was doing some VSPR questions earlier that asked me to draw the Lewis structure but I kept putting oxygen as the central atom when it was suppose to be Cl as the central atom. Why would Cl be the central atom and not O? Thanks!

2c_britneyly
Posts: 62
Joined: Fri Sep 28, 2018 12:16 am

Re: Central atoms in Lewis Structure

Postby 2c_britneyly » Sat Nov 24, 2018 2:43 pm

The general rule is that the least electronegative atom is placed in the center. So if you're drawing a Lewis structure that has carbon and oxygen atoms, carbon will be the central atom. However, for elements in row 3 and beyond with available space in the d shell, they can have expanded octets and will then become the central atom. This would be the case when Cl is the central atom and not O, since oxygen atoms can make only 2 bonds. Cl can make more bonds and accommodate more atoms.


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