✔ 最佳答案
The very simple technique I use to work these out is:
triple bond = sp hydridised
double bone = sp2
single bonds = sp3
In a more physical chemical term, we need to think about the molecule as a whole. ie. not just the central atom but the substitutents attached to it. The reason why we have sp-x is because in a molecule, the s-orbital and the p-orbitals are 'mixed' when bonding (ie. sharng electrons). The 1s-orbital is always filled, and the rest of the electrons are spread out into the available 2s and 2p-orbitals, which are px, py, and pz (because 1s only holds 2 electrons, most molecules have more than 2 electrons)
So, instead of: 1s, 2s, 2px, 2py, 2pz
we'd have: 1s, 2s, 2spx, 2spy, 2spz <-- this is the case of sp3 hybrid, because 2s mixes with all the p-orbitals when forming a bond.
In the case of sp2, the 2s orbital obly mixes wth two p-orbitals, and sp = 2s mixes with just one p-orbital
To go further, it would require 'Molecular Orbital Theory' to explain everything, which includes concepts such as bonding and non-bonding orbitals.
Hope that makes sense.
2008-05-17 21:12:35 補充：
Oops, examples:
CH4 = sp3 -- 1s orbital filled, the rest spreads out into 2s, 2px, 2py and 2pz. When a bond is formed, the electrons are promoted to the higher orbital due to energy put into the system.
2008-05-17 21:12:42 補充：
Ethylene = sp2 -- same reason but only two p-orbitals are occupied.
Hybridisation also considers the orientation the atom are most comfortable in, partly the reason for the different orbitals being mixed during bonding.
