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Tetrahedral vs Trigonal Pyramid

Posted: Sun Nov 12, 2017 5:17 pm
by Tylor McGrew 1J
I am confused as to when a Lewis Structure is identified as Tetrahedral or Trigonal Pyramid. Both have 4 bonds/lone pairs so how is one to know which is which?

Re: Tetrahedral vs Trigonal Pyramid

Posted: Sun Nov 12, 2017 5:27 pm
by Ya Gao
Tetrahedral is when the central atom has only four bonds around it(no lone pairs) and trigonal pyramid is when the central atom has three bonds and one lone pair around it. Hope it helps.

Re: Tetrahedral vs Trigonal Pyramid

Posted: Sun Nov 12, 2017 5:50 pm
by Danah Albaaj 1I
Another way to think of it is trigonal pyramidal is a tetrahedral shape that has lost a bond and replaced it with a lone pair. You can see it when you look at the VSEPR notation for both shapes, tetrahedral is AX4 while trigonal pyramidal is AX3E.