Hybridization describes the mixing of atomic orbitals to form new orbitals for bonding. The type of hybridization (sp, sp², sp³) directly correlates with molecular geometry and bond angles.
Start with Lewis structures and VSEPR predictions, then determine hybridization type from geometry.
Thinking hybridization happens before bonding; confusing the number of hybrid orbitals with bond count.
You already know from VSEPR theory that electron groups around a central atom arrange themselves to minimize repulsion, producing geometries like linear, trigonal planar, and tetrahedral. Hybridization explains *why* bonds point in those directions by describing how atomic orbitals mix to create new orbitals oriented toward bonding partners.
Consider carbon in methane (CH₄). A ground-state carbon atom has the configuration 1s² 2s² 2p², with two unpaired electrons in separate 2p orbitals. This suggests carbon should form only two bonds — but it forms four. The resolution is that one 2s and three 2p orbitals hybridize (mathematically mix) to produce four equivalent sp³ hybrid orbitals, each containing one electron and pointing toward the corner of a tetrahedron. The energy cost of mixing is more than repaid by forming four strong bonds instead of two. The resulting bond angle is 109.5°, exactly matching VSEPR's prediction for four electron groups.
The pattern extends to other hybridization types. When carbon forms a double bond (as in ethylene, C₂H₄), it needs only three σ-bonding directions in a plane. One 2s and two 2p orbitals mix to form three sp² hybrid orbitals arranged in a trigonal planar geometry (120° apart), while the remaining unhybridized p orbital sticks out perpendicular to the plane and forms the π bond of the double bond. In a triple bond (as in acetylene, C₂H₂), one 2s and one 2p orbital mix to give two sp hybrid orbitals pointing in opposite directions (180°, linear), while two unhybridized p orbitals form two π bonds. The rule is simple: count the number of electron groups (σ bonds + lone pairs) around an atom — 4 groups means sp³, 3 means sp², 2 means sp.
A critical point: hybridization is a model that describes the *result* of bonding, not a process that happens before bonds form. Atoms do not first hybridize and then look for partners — the mixing of orbitals occurs because it produces a lower-energy bonded state. Also, the number of hybrid orbitals equals the number of atomic orbitals that mixed, and each hybrid orbital holds either a bonding pair or a lone pair. Lone pairs occupy hybrid orbitals just like bonding pairs do: ammonia (NH₃) is sp³ with three bonding pairs and one lone pair, giving a tetrahedral electron geometry but a pyramidal molecular shape — consistent with what VSEPR already told you.
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