Ch10 Vocab Flashcard

Lewis structure; Lewis formula
a structural formula consisting of electron-dot symbols, with lines as bonding pairs and dots as lone pairs
resonance structure; resonance form
one of two or more Lewis structures for a molecule that cannot be adequately depicted by a single structure. Resonance structures differ only in the position of bonding and lone electron pairs.
resonance hybrid
The weighted average of the resonance structures of a molecule.
(electron-pair) delocalization
The process by which electron density is spread over several atoms rather than remaining between two.
formal charge
The hypothetical charge on an atom in a molecule or ion, equal to the number of valence electrons minus the sum of all the unshared and half the shared valence electrons.
electron deficient
Referring to a bonded atom, such as Be or B, that has fewer than eight valence electrons.
free radical
A molecular or atomic species with one or more unpaired electrons, which typically make it very reactive.
expanded valence shell
A valence level that can accommodate more than 8 electrons by using available d orbitals; occurs only for elements in Period 3 or higher.
valence-shell electron-pair repulsion (VSEPR) theory
a model explaining that the shapes of molecules and ions result from minimizing electron-pair repulsions around a central atom.
molecular shape
The three-dimensional structure defined by the relative positions of the atomic nuclei in a molecule.
bond angle
The angle formed by the nuclei of two surrounding atoms with the nucleus of the central atom at the vertex.
linear arrangement
The geometric arrangement obtained when two electron groups minimize their separation around a central atom.
linear shape
A molecular shape formed by three atoms lying in a straight line, with a bond angle of 180 degrees (shape class AX_2 or AX_2_E_3).
trigonal planar arrangement
The geometric arrangement formed when three electron groups maximize their separation around a central atom.
bent shape
A molecular shape that arises when a central atom is bonded to two other atoms and has one or two lone pairs; occurs as the AX_2E shape class (bond angle < 120 degrees) in the trigonal planar arrangement and as the AX_2E_2 shape class (bond angle < 109.5 degrees) in the tetrahedral arrangement.
tetrahedral arrangement
The geometric arrangement formed when four electron groups maximize their separation around a central atom; when all four groups are bonding groups, the molecular shape is tetrahedral (AX_4; ideal bond angle 109.5 degrees)
trigonal pyramidal shape
A molecular shape (AX_3) caused by the presence of one lone pair in a tetrahedral arrangement.
trigonal bipyramidal arrangement
The geometric arrangement formed when five electron groups maximize their separation around a central atom. When all five groups are bonding groups, the molecular shape is trigonal bipyramidal (AX_5; ideal bond angles, axial-center-equatorial 90 degrees and equatorial-center-equatorial 120 degrees)
equatorial group
An atom (or group) that lies in the trigonal plane of a trigonal bipyramidal molecule, or a similar structural feature in a molecule.
axial group
An atom (or group) that lies above or below the trigonal plane of a trigonal bipyramidal molecule, or a similar structural feature in a molecule.
seesaw shape
A molecular shape caused by the presence of one equatorial lone pair in a trigonal bipyramidal arrangement (AX_4E)
T shape
A molecular shape caused by the presence of two equatorial lone pairs in a trigonal bipyramidal arrangement (AX_3E_2)
octahedral arrangement
The geometric arrangement obtained when six electron groups maximize their space around a central atom; when all six groups are bonding groups, the molecular shape is octahedral (AX_6; ideal bond angle = 90 degrees)
square pyramidal shape
A molecular shape (AX_4E_2) caused by the presence of two axial lone pairs in an octahedral arrangement.
molecular polarity
The overall distribution of electronic charge in a molecule, determined by its shape and bond polarities.
dipole moment
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