[Chaste]

is the point group of Na₂O D-infinity-H or C_2v? and why?

[AWK]

Na₂O should be a ionic compounds. Point group can be assigned to a molecule. In this case you should know the crystal structure of Na₂O. But for H₂O you can assign point group easily.

[Chaste]

I'm sorry. I didn't really get anything from your reply. I know water is C2v.

[Borek]

Perhaps AWK was not perfectly clear. What he means is that Na₂O is an ionic compound and as such doesn't have separate molecules. However, it does have crystallic ctructure. So, you can't talk about symmetry of the molecule (as it doesn't exist), but you can analyse symmetry of the crystal.

In the case of water separate molecules do exist, so you can assign them a point group.

[Chaste]

oh i see... sorry for the lack of background knowledge. However, i need to find the point group so as to draw the molecular orbital diagram with the symmetry labels for each MOs.

[Chaste]

so which point grp shd i assign na2o for its crystalline structure?

[AWK]

O_h
But note - molecular diagram is for molecules, not ions

[Chaste]

can we just isolate the na2o out and determine its point grp?
cuz.. i need to plot the molecular diagram as a homework

[AWK]

Crystal structure of Na₂O - cubic system (oxygen red, sodium -blue)