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### tetrahedral vs trigonal planar

Posted: Fri Nov 16, 2018 2:47 pm
I am having trouble distinguishing between tetrahedral and trigonal planar, how can I know which the Lewis structure is?

### Re: tetrahedral vs trigonal planar

Posted: Fri Nov 16, 2018 2:52 pm
Tetrahedral geometry requires four atoms bonded to a central atom. Trigonal planar only has three atoms bonded to the central atom.

### Re: tetrahedral vs trigonal planar

Posted: Fri Nov 16, 2018 2:52 pm
tetrahedral has 4 bonding regions, while trigonal planar has only 3. When you look at the lewis structure of the central atom, look at how many bonding regions it has.

### Re: tetrahedral vs trigonal planar

Posted: Fri Nov 16, 2018 4:30 pm
You can simply distinguish them with the number of atoms as the above posts say, or imagine the shape based on Lewis structures. Pay attention to lone pairs.

### Re: tetrahedral vs trigonal planar

Posted: Fri Nov 16, 2018 4:40 pm
So what helps best is to draw the Lewis structure of the compound. So you have your central atom and typically the other surrounding atoms. If there are no lone pairs and it has 4 surrounding atoms it is tetrahedral (tetra=4). However, if it is trigonal planar (tri=3) then it only has 3 surrounding atoms. Keep in mind lone pairs change the shape because of electron repulsion.

### Re: tetrahedral vs trigonal planar

Posted: Fri Nov 16, 2018 11:57 pm
How many lone pairs are possible when the molecule is in the trigonal planar shape?

### Re: tetrahedral vs trigonal planar

Posted: Sat Nov 17, 2018 10:30 am
Tetrahedral means that there are four atoms bound around a central atom. Trigonal planar is when there are three atoms bound around a central atom. You can memorize the A, X, and E for each structure to better identify them in the future.

### Re: tetrahedral vs trigonal planar

Posted: Sat Nov 17, 2018 5:36 pm
Danny Elias Dis 1E wrote:How many lone pairs are possible when the molecule is in the trigonal planar shape?

There can be 3 regions for this shape, but I think we've only seen molecules in this shape with one lone pair, e.g. SO2, a bent shape.

### Re: tetrahedral vs trigonal planar

Posted: Sat Nov 17, 2018 6:11 pm
What helps me is looking at the VSEPR formula. They are distinct from one another.

### Re: tetrahedral vs trigonal planar

Posted: Sat Nov 17, 2018 6:38 pm
It helps me to just remember that tetrahedral has a general formula of AX4 while trigonal planar has a formula of AX3. (A being the central atom and X being bound atoms)