# 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!

Apr 24, 2018

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

#### Explanation:

For ${\text{NF}}_{3}$, 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.

${\text{OF}}_{2}$ 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.

$\text{H"_2"S}$ will be just like $\text{OF"_2}$ 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.