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(1) Hybridization is the process of mixing
the atomic orbitals in an atom (usually
the central atom) to generate a set of
new atomic orbitals.
8-2.4 Hybrid Orbital Theory
Ⅰ. The Central Themes of Hybridization Theory
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(2) The new atomic orbitals are called hybrid orbitals. Hybrid orbital is atomic orbitals obtained when two or more nonequivalent orbitals of the same atom combine, are then used to form covalent bonds.
(3) The number of hybrid orbitals generated is equal to the number of atomic orbitals.
(4) The spatial orientation of these new orbitals lead to more stable bonds and are consistent with the observed molecular shapes.
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The following points are useful for an understanding of hybridization
(1) The concept of hybridization does not apply to isolated atoms. It is used only to explain a bonding scheme in a molecule.(2) Hybrid orbital is not a pure atomic orbital. Hybrid orbitals have very different shapes from pure atomic orbitals.
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(4) Covalent bonds in polyatomic molecules are formed by the overlap of a hybrid orbital and a pure atomic orbital, or of two hybrid orbitals.
(3) All the hybrid orbitals are equivalent in every respect, except in their relative orientations in space.
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Ⅱ. Types of Hybrid Orbitals
1. sp Hybridization
One s orbital and one p orbital form twosp hybrid orbital
Hybridization of all s orbital and a p orbital (of the same atom) produce two sp hybrid orbitals. The twosp hybrid orbitals have a linear arrangement.
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• BF3 molecules
• 5B: 2s2 2p1
excitated
hybridizesp2 hybrid orbital
↑↓ ↑↓ ↑↓
↑↑↓
↑ ↑↑
↑ ↑ ↑
BF3
sp2-p
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Hybridization
Equivalent hybridization
sp: BeCl2
sp2: BF3 , C2H4
sp3: CH4 , CCl4
sp3: NH3 , H2ONonequivalent hybridization
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• NH3 moleculeCentral atom N7N: 1s2 2s2 2p3
hybridize
sp3 Hybrid orbital(one lone pair electrons)
Nonequivalent hybridization
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hybridize
sp3 Hybrid orbital(two lone pair electrons)
• H2O moleculeCentral atom O
8O: 1s2 2s2 2p4
23bonding-pair vs. bonding
pair repulsionlone-pair vs. bonding
pair repulsion < < lone-pair vs. lone pairrepulsion
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sp2 Hybridization of Ethylene
• 6C: 2s2 2p2 CH2=CH2 (ethylene)
excitated
hybridizesp2 hybrid orbital
2py orbital
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sp Hybridization of Acetylene
6C: 2s2 2p2 CH ≡ CH (acetylene)
excitated
hybridize
↑
↑↓ ↑↓
↑
sp hybrid orbital
↑↓ ↑↓