[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.
p: [Ne]   3s:    3p:      . 

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?

[Hunter2]

Describe PCl₅

[kougou]

Describe PCl₅

p only has 3 unbound p orbital.
Therefore, you need sp2d2 hybri orbitial

[Hunter2]

Correct.