[RenderedAwake]

Ok...so I'm doing some pre-organic studying, and have come to the topic of hybridization. I understand the basic concepts, such as the following: sp (linear, 180 degrees, 2 electron groups), sp2 (trigonal planar, 120 degrees, 3 electron groups), sp3 (tetrahedral, 109.5 degrees, 4 electron groups). So if I have a stucture, I can figure out what the hybridization is.. but what I have trouble with is understanding what is happening.

For instance, in sp3 there are 4 hybridized atoms. However, you are combining an S orbital, and then the Px, Py, and Pz orbitals.  If I think about it, Px has 2 lobes, Py has 2 lobes, and Pz has 2 lobes, plus the 1 "lobe/circle" from the S orbital. Well 2+2+2+1 = 7..however, in all the pictures, there are only 4 lobes seen.. (for instance: http://www.dlt.ncssm.edu/TIGER/diagrams/vsepr_pix/sphybrid/Sp3.jpg )  Where did the rest of them go??.   

If anyone could explain this to me... I'd be quite grateful.!.

[enahs]

And s-orbital is "positive" everywhere. A p-orbital has a "positive" and "negative" end. When the P and S orbitals mix, there is cancellation of "positive and negative".

http://www.wellesley.edu/Chemistry/chem120/hybrids.html

[FeLiXe]

each lobe is basically a combination of one s orbital and one p orbital. I made something in Javascript that supposed to show that, link.

out of the four orbitals (three p and one s) we make 4 such one lobed orbitals. that's why it's just four lobes.