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19 Cards in this Set
- Front
- Back
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valence bond theory or VB theory
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This theory is used to explain molecular shapes. Its central idea is as follows: A covalent bond forms when orbital of two atoms overlap and the overlap region, which is between the nuclei is occupied by a pair of electrons.
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hybridization
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Valence atomic orbitals in a molecule are different from those in the isolated atoms. The atomic orbitals mix in specific combinations in a process called hybridization.
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hybrid orbital
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The new atomic orbital in an atom in a molecule resulting from the mixing of atomic orbitals is called a hybrid orbital
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sp hybrid orbital
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One s and one p orbital in the central atom of a molecule mix to form two sp hybrid orbitals. They lie 180° apart.
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sp2 hybrid orbital
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One s and two p orbitals in the central atom of a molecule mix to form three sp2 hybrid orbitals. They lie 120° apart.
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sp3 hybrid orbital
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One s and three p orbitals in the central atom of a molecule mix to form four sp3 hybrid orbitals. They lie 109.5° apart.
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sp3d hybrid orbital
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One s, three p and one d orbitals in the central atom of a molecule mix to form five sp3d hybrid orbitals. They lie 120° and 90° apart.
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sp3d2 hybrid orbital
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One s, three p and two d orbitals in the central atom of a molecule mix to form six sp3d2 hybrid orbitals. They lie 90° apart.
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sigma bond (σ)
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Bonds resulting from end-to-end overlap is called a sigma bond. Its highest electron density is along the bond axis and it is cylindrically symmetric.
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pi (π) bond
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Bonds resulting from sid-to-side overlap is called a pi bond. A double bond always has one sigma and one pi bonds. A triple bond has one sigma and two pi bonds. Pi bonds do not have free rotation along the axis joining the two nuclei.
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molecular orgbital (MO) theory
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This theory explains not just molecular structrure but also magnetic properties in a molecule. It assumes electron delocalization in a molecule, versus the electron localization assumption in the VB theory.
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molecular orbital (MO)
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Just as atoms have atomic orbitals, the MO theory assumes that molecules have molecular orbitals of given energy and shape.
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bonding MO
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Adding the atomic wavefunctions together forms a bonding MO, which has a region of high electron density between the nuclei.
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antibonding MO
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Subtracting the wavefunctions from each other results in an antibonding MO which has a region of zero electron density (a node) between the nuclei.
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sigma MO (σ)
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The cylindrically symmetric orbitals are referred to as sigma MOs. The bonding states are referred to as sigma states while the antibonding states are referred to as sigma * states.
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molecular orbital (MO) diagram
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It is an orbital box diagram showing the atomic states and the MOs with their relative energies and with electrons filled in.
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MO bond order
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Bond order = 1/2 [(# bonding e-s)-(# anti-bonding e-s)]
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homonuclear diatomic molecule
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Thia molecule is composed of two identical atoms.
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pi (π) MO
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The molecular orbitals formed from side-to-side overlap of atomic orbitals (eg. p-orbitals) result in the formation of pi MOs.
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