Question

Determine the number of electron groups around the central atom for each of the following molecules?

Hi! So like my question says, i need to determine the number of electron groups around the central atom for each of the following molecules:
NF3
OF2
H2S

I have tried entering the following and have gotten them wrong.
NF3 = 3
OF2 = 2
H2S = 2

Any explanation you could give would be greatly appreciated, thank you!

Answer 1

Electron groups are lone pairs and/or bonds (since we explain bonds as a pair of shared electrons).

Explanation:

For `"NF"_3`, the Lewis Structure will give you something like Nitrogen in the center with 3 bonds to F atoms, and 1 lone pair(I don't know how to draw structures on here).
If you look at the Nitrogen, it has 4 different electron groups around it (3 from the bonds, 1 from lone pair). You can re-draw the bonds as pairs of Electrons - this might help show how there are 4 groups.

![https://chem.libretexts.org/LibreTexts/University_of_California%2C_Santa_Cruz/UCSC%3A_Chem_1B-AL_(Mednick)/Worksheets%3A_General_Chemistry/Lewis_Dot_Structures_(Worksheet)/Solutions]()

`"OF"_2` will be the same thing, except it will have 2 bonds to 2 fluorine atoms, and 2 lone pairs. There are a total of 4 electron groups around Oxygen.


`"H"_2"S"` will be just like `"OF"_2"` above. 2 bonds to Hydrogens and 2 lone pairs. This gives 4 electron groups around S.

![)

All of these have electron geometry of "Tetrahedral".
Molecular Geometry will be: Trigonal Pyramidal, Bent, Bent.