Molecular Geometry and Bond Theories – Flashcards
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| bond angles |
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| the angles made by the lines joining the nuclei of the atoms in a molecule |
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| VSEPR model |
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| a model that accounts for the geometric arrangements of shared and unshared electron pairs around a central atom in terms of the repulsions between electron pairs |
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| electron domains |
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| in the VSEPR model, a region about a central atom in which an electron pair is concentrated |
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| bonding pairs |
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| in a Lewis structure a pair of electrons that is shared by two atoms |
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| nonbonding pairs |
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| in a Lewis structure a pair of electrons assigned completely to one atom; also called lone pair |
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| electron-domain geometry |
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| the 3D arrangement of the electron domains around an atom according to the VSEPR |
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| molecular geometry |
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| the arrangement in space of the atoms of a molecule |
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| bond dipoles |
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| the dipole moment that is due to unequal electron sharing between two atoms in a covalent bond |
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| valence-bond theory |
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| a model of chemical bonding in which an electron-pair bond is formed between two atoms by the overlap of orbitals on the two atoms |
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| hybrid orbitals |
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| an orbitals that results from the mizing of different kinds of atomic orbitals on the same atoms; for example, an sp3 hybrid results from the mixing, or hybridizing, of one s orbital and three p orbitals |
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| hybridization |
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| the mixing of different types of atomic orbitals to produce a set of equivalent hybrid orbitals |
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| sigma bonds |
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| a covalent bond in which electron density is concentrated along the internuclear axis |
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| pi bonds |
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| a covalent bond in which electron density is concentrated above and below the internuclear axis |
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| delocalized electrons |
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| electrons that are spread over a number of atoms in a molecule or a crystal rather than localized on a single atom or pair of atoms |
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| molecular orbital theory |
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| a theory that accounts for the allowed states for electrons in moleucles |
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| molecular orbitals (MOs) |
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| an allowed state for an electron in a molecule; according to molecular orbital theory, an MO is entirely analogous to an atomic orbital, which is an allowed state for an electron in an atom; most boding molecular orbitals can be classified of sigma or pi, depending on the disposition of electron density with respect to the internuclear axis |
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| bonding molecular orbital |
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| a molecular orbital in which the electron density is concentrated in the internuclear region; the energy of a bonding molecular orbital is lower than the energy of the separate atomic orbitals from which it forms |
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| antibonding molecular orbital |
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| a molecular orbital in which electron density is concentrated outside the region between the two nuclei of bonded atoms; such orbitals are less stable than bonding molecular orbitals |
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| sigma molecular orbitals |
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| a molecular orbital that centers the electron density about an imaginary line passing through two nuclei |
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| energy-level diagram |
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| a diagram that shows the energies of molecular orbitals relative to the atomic orbitals from which they are derive |
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| molecular orbital diagram |
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| a diagram that shows the energies of molecular orbitals relative to the atomic orbitals from which they are derived |
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| bond order |
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| the number of bonding electron pairs shared between two atoms, minus the number of antibonding electron pairs: bond order = (number or bonding electrons-number of antibonding electrons)/2 |
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| pi molecular orbitals |
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| a molecular orbital that concentrates the electron density on opposite sides of an imaginary line that passes through the nuclei |
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| paramagnetism |
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| a property that a substance possesses if it contains one or more unpaired electrons; a paramagnetic substance is drawn into a magnetic field |
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| diamagnetism |
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| a type of magnetism that causes a substance with no unpaired electrons to be weakly repelled from a magnetic field |
