How to Explain Hybridization in Chemistry
Valence bond (VB) theory is a useful way to explain many properties of molecules. One of the most important concepts in VB theory is orbital hybridization, which is used to explain molecular geometry in organic chemistry. Mathematically, VB theory is complex, but it's also possible to understand it in a very simple qualitative way, and this is how chemists generally use it, because molecular orbital (MO) theory has proven to be superior for actually performing calculations.
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Instructions
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Recall that in quantum mechanics, the state of a system of particles like an atom is described by a wavefunction. The wavefunction must satisfy certain conditions, and therefore the atom can only exist in certain states. The wavefunctions of a hydrogen atom are called atomic orbitals. It's not possible to find an exact solution for the wavefunction for helium and larger atoms, but these can be approximated as combinations of hydrogen-like orbitals, and so electrons in an atom of carbon or another element larger than helium are described as occupying atomic orbitals that resemble those you can define for the hydrogen atom.
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Remember that the absolute square of the wavefunction gives the probability you will find an electron at any location. For each orbital, there is a higher probability of finding the electron in some places than in others, so each type of orbital has a corresponding shape in 3D. S-orbitals are spherical, while p-orbitals have two lobes on either side of a plane and are often described as dumbbell-shaped.
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Recognize that you can combine multiple valence orbitals to form so-called hybrid orbitals. Any time you combine X number of orbitals, you will end up with X number of hybrid orbitals. If you combine an s and a p orbital, for example, you'll end up with 2 hybrid orbitals, because you had 2 orbitals to start with.
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Notice that for carbon and other period 2 elements (the elements for which VB theory is typically used), you have a 2s orbital and 3 2p orbitals in the valence shell. These are the valence orbitals that will participate in bonding with other atoms. There are three different hybridization schemes you can make with these valence orbitals. You could combine an s-orbital and a p-orbital to form an sp-hybrid. You could combine an s-orbital and 2 p-orbitals to make an sp2-hybrid. Finally, you could combine an s-orbital and 3 p-orbitals to make an sp3-hybrid.
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Learn the shapes and configurations associated with each of these hybridization schemes. An sp3-hybrid has four bowling-pin shaped orbitals pointing toward the corners of an imaginary tetrahedron. An sp2-hybrid has three bowling-pin shaped orbitals pointing toward the corners of an equilateral triangle, all of them located in the same plane, with an unhybridized p-orbital pointing straight up and down, perpendicular to the hybrid orbitals. Finally, an sp-hybrid has two lobes pointing in opposite directions, while the two unhybridized p-orbitals lie along axes perpendicular to the sp-hybrid orbitals and to each other.
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