when to use HYBRIdiZED ORBITAL?

kougou

Hi.

I am wondering when should we use hybridized orbital?
For PH3, we don't use hybridized orbital because it could be described by the valence shell method.
The valence shell orbital diagram:
p: [Ne] 3s:up down 3p: up up up

And we have 3 up. so the 3 extra electrons from hydrogen could fit into there. Therefore we don't need hybridized orbital.
But when do we need it?

DrDu

You most need it in the case of tetravalent carbon to get four equivalent bonds using valence bond theory. Most other molecules like NH3, H2O etc. can be described well using only their p-orbitals in bonding.

dextercioby

Surely we do need hybridized orbitals. The classical Lewis structure is not true at quantum level, the bonding angle between the overlapping electronic probability clouds is not 90deg as predicted by the classical Lewis structure, but approx. 107deg.

http://en.wikipedia.org/wiki/Trigona...cular_geometry

DrDu

That the angle is off from 90 deg, does not mean that you have to use hybrid orbitals, especially in molecules like PH3 where the radii of the s and p orbitals on Phosphorus are too different to make useful hybrids. The bond angle in PH3 is only 93.5 deg.

kougou

Hi. I just googled it. Most ppl from the web said for PH3, you will have sp3 hybri orbital, but then from the text, it clearly identify that it doesn't need to use hybri orbital.
So, what do you think?

Can I go wrong if I assume everything will use hybri orbital?

DrDu

Then why do you ask?

kougou

No. I mean. I still unclear whether it should use hybri or not.
The text says no.
Other ppl say yes.

dextercioby

People may say whatever they want. I would go for a textbook over some 'hearsay' on the (free) internet.

And please, make an effort to write <people>.