[Michael M.]

What is the molecular geometry around a central atom that is sp2
hybridized, has three sigma bonds, and one pi bond?

I think that the answer is trigonal planal, there are three sigma bonds and one pi bond.  There is no lone pair electrons which means all sides are the same.  I would greatly appreciate any input.


a. trigonal-planar
b. trigonal-pyramidal
c. bent
d. T-shaped
e. tetrahedral

[Ben Bob2]

Forum rules request that you attempt a problem first and show your work before asking a question.
Tell us what you think the answer is and explain how you got to that conclusion.

[Michael M.]

Forum rules request that you attempt a problem first and show your work before asking a question.
Tell us what you think the answer is and explain how you got to that conclusion.

What is the molecular geometry around a central atom that is sp2
hybridized, has three sigma bonds, and one pi bond?

a. trigonal-planar
b. trigonal-pyramidal
c. bent
d. T-shaped
e. tetrahedral

I think that the answer is trigonal planal, there are three sigma bonds and one pi bond.  There is no lone pair electrons which means all sides are the same.  I would greatly appreciate any input.

[Ben Bob2]

I think that the answer is trigonal planal, there are three sigma bonds and one pi bond.  There is no lone pair electrons which means all sides are the same.  I would greatly appreciate any input.

Yes, that's the same conclusion I came to; there are three bonds from a central atom and no lone pairs, making this an AX₃ geometry, therefore trigonal planer.

[TntNut]

I had the same question but I am torn between bent and triangular planar, I tend to believe it's bent because a pi bond means there is a double bond, this would increase the electron density on one side which will decrease the angle between the other two sigma bonds, and isn't that the definition of a bent molecule.
I know that 2 covalent bonds will not have the same effect on decreasing the angle between two bonds as much as an unbounded pair of electrons, but I still think it will be bent and the angles will not be equal.

[AWK]

cf. ethene (ethylene)

[TntNut]

I am a bit confused by your reply, could you explain further? (sorry I'm not that great at chem, high school student taking first year college chem)

[AWK]

Both carbon atoms in  ethene - 3 sigma bonds and 1 pi-bond.
Other examples: carbonate dianion, nitrate(V) anion.

[TntNut]

I looked further into it and it turns out it was trigonal planar making my hypothesis (that it is bent due to its double bond) invalid, here's an article that describes the structure of ethene: http://chem.libretexts.org/Core/Organic_Chemistry/Alkenes/Properties_of_Alkenes/Structure_and_Bonding_in_Ethene-The_Pi_Bond

[AWK]

Small difference in angles are unimpotrant. 120 Degrees describes an idealized geometry. Much more important is flatness of molecule. Check for example azobenzene.
Distortions of angles come from repulsions of bonds electrons.