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Molecular Geometry and Bond Theories
chapter 9
25
Chemistry
12th Grade
01/07/2013

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Term
bond angles
Definition
the angles made by the lines joining the nuclei of the atoms in a molecule
Term
VSEPR model
Definition
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
Term
electron domains
Definition
in the VSEPR model, a region about a central atom in which an electron pair is concentrated
Term
bonding pairs
Definition
in a Lewis structure a pair of electrons that is shared by two atoms
Term
nonbonding pairs
Definition
in a Lewis structure a pair of electrons assigned completely to one atom; also called lone pair
Term
electron-domain geometry
Definition
the 3D arrangement of the electron domains around an atom according to the VSEPR
Term
molecular geometry
Definition
the arrangement in space of the atoms of a molecule
Term
bond dipoles
Definition
the dipole moment that is due to unequal electron sharing between two atoms in a covalent bond
Term
valence-bond theory
Definition
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
Term
hybrid orbitals
Definition
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
Term
hybridization
Definition
the mixing of different types of atomic orbitals to produce a set of equivalent hybrid orbitals
Term
sigma bonds
Definition
a covalent bond in which electron density is concentrated along the internuclear axis
Term
pi bonds
Definition
a covalent bond in which electron density is concentrated above and below the internuclear axis
Term
delocalized electrons
Definition
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
Term
molecular orbital theory
Definition
a theory that accounts for the allowed states for electrons in moleucles
Term
molecular orbitals (MOs)
Definition
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
Term
bonding molecular orbital
Definition
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
Term
antibonding molecular orbital
Definition
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
Term
sigma molecular orbitals
Definition
a molecular orbital that centers the electron density about an imaginary line passing through two nuclei
Term
energy-level diagram
Definition
a diagram that shows the energies of molecular orbitals relative to the atomic orbitals from which they are derive
Term
molecular orbital diagram
Definition
a diagram that shows the energies of molecular orbitals relative to the atomic orbitals from which they are derived
Term
bond order
Definition
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
Term
pi molecular orbitals
Definition
a molecular orbital that concentrates the electron density on opposite sides of an imaginary line that passes through the nuclei
Term
paramagnetism
Definition
a property that a substance possesses if it contains one or more unpaired electrons; a paramagnetic substance is drawn into a magnetic field
Term
diamagnetism
Definition
a type of magnetism that causes a substance with no unpaired electrons to be weakly repelled from a magnetic field
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