Chemistry AP Chapter 9 Vocab

bond angles

bond angles

The angles made by the lines joining the nuclei of the atoms in a molecule.

valence-shell electron-pair repulsion (VSEPR) model

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.

bonding pair

a single covalent bond is formed between two atoms when a pair of electrons occupies the space between the atoms.

a nonbonding pair

r (or lone pair) of electrons,

electron domain

defines a region in which the electrons are most likely to be found.

electron-domain geometry

The arrangement of electron domains about the central atom of an ABn molecule or ion

molecular geometry

the arrangement of only the atoms in a molecule or ion—any nonbonding pairs in the molecule are not part of the description of the molecular geometry.

bond dipole

s the dipole moment due only to the two atoms in that bond. (specfic bond)

valence-bond theory

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.

hybrid orbital

An orbital that results from the mixing of different kinds of atomic orbitals on the same atom. For example, an sp3 hybrid results from the mixing, or hybridizing, of one s orbital and three p orbitals.

hybridization

The mixing of different types of atomic orbitals to produce a set of equivalent hybrid orbitals.

hypervalent

have more than an octet of electrons around the central atom

sigma molecular orbital

A molecular orbital that centers the electron density about an imaginary line passing through two nuclei

pi bond

A covalent bond in which electron density is concentrated above and below the internuclear axis

pi molecular orbital

A molecular orbital that concentrates the electron density on opposite sides of an imaginary line that passes through the nuclei.

delocalized electrons

Electrons that are spread over a number of atoms in a molecule or a crystal rather than localized on a single atom or a pair of atoms

molecular orbital (MO)

An allowed state for an electron in a molecule. According to molecularorbital theory, a molecular orbital is entirely analogous to an atomic orbital, which is an allowed state for an electron in an atom. Most bonding molecular orbitals can be classified as s or p, depending on the disposition of electron density with respect to the internuclear axis.

molecular-orbital diagram

A diagram that shows the energies of molecular orbitals relative to the atomic orbitals from which they are derived; also called an energy-level diagram.

molecular-orbital theory

A theory that accounts for the allowed states for electrons in molecules.

antibonding molecular orbital

A molecular orbital in which electron density is concentrated outside the region between the two nuclei of bonded atoms. Such orbitals, designated as s* or p*, are less stable (of higher energy) than bonding molecular orbitals.

bonding molecular orbital

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.

nodal plane

Antibonding orbitals invariably have a plane in the region between the nuclei where the electron density is zero

bond order

The number of bonding electron pairs shared between two atoms, minus the number of antibonding electron pairs: bond order = (number of bonding electrons - number of antibonding electrons)/

sigma bond

A covalent bond in which electron density is concentrated along the internuclear axis.

paramagnetism

A property that a substance possesses if it contains one or more unpaired electrons. A paramagnetic substance is drawn into a magnetic field.

diamagnetism

A type of magnetism that causes a substance with no unpaired electrons to be weakly repelled from a magnetic field. (