I was solving an exercise my teacher asked us, to determinate the hibridization of the molecules. He give the molecule and I have to tell which hibridization it is. I want to know if I can do this to every molecule, I mean, are all molecules in the world hybridized? If so, why do we have to learn the geometry of s, p, d and f orbitals if all that works is the VSPER geometry for hybridized orbitals? I tried to see if the hybridized theory works and what I found out? Water hydrogen angle is 104.5 degrees (~109.5) NH3 angle is 107 degrees (~109.5) Although, when I compare the other molecules in further periods, it seems that the hybridization decreeases. H2S is 92.1 degrees H2Se is 91 degrees H2Te is 90 degrees PH3 93.5 degrees AsH3 91.8 degrees Why does it occur? Why are small molecules hybridized and bigger aren't? How can I know when a molecule will hibridizate?