Chemistry - Chapter 10 Vocab

Front 1

Lewis structure
(Lewis formula)

Back 1

a structural formula consisting of electron-dot symbols, with lines as bonding pairs and dots as lone pairs

Front 2

resonance structure
(resonance form)

Back 2

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

Front 3

resonance hybrid

Back 3

the weighted average of the resonance structures of a molecule

Front 4

electron-pair delocalization

Back 4

the process by which electron density is spread over several atoms rather than remaining between the two

Front 5

formal charge

Back 5

the hypothetical charge on an atoms 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

Front 6

electron deficient

Back 6

referrring to a bonded atom, such as Be or B, that has fewer than eight valence electrons

Front 7

free radical

Back 7

a molecular or atomic species with one or more unpaired electrons, which typically make it very reactive

Front 8

expanded valence shell

Back 8

a valence level that can accomodate more than eight electrons by using available d orbials (only elements in period 3 or higher)

Front 9

valence-shell electron-pair repulsion

(VSEPR)

Back 9

a model explaining that the shapes of molecules and ions result from minimizing electron-pair repulsions around a central atom

Front 10

molecular shape

Back 10

the three-dimensional structure defined by the relative positions of the atomic nuclei in a molecule

Front 11

bond angle

Back 11

the angle formed by the nuclei of two surrounding atoms with the nucleus of the central atom at the vertex

Front 12

linear arrangement

Back 12

the geometric arrangement obtained when two electron groups maximize their separation around a central atom

Front 13

linear shape

Back 13

a molecular shape formed by three atoms lying in a striaght line, with a bond angle of 180 degrees (shape class AX2 or AX2E3)

Front 14

trigonal planar arrangement

Back 14

the geometric arrangement formed when three electron groups maximize their separation around a central atom

Front 15

bent shape
(V shape)

Back 15

a molecular shape that arises when a central atom is bonded to two other atoms and has one or wo lone pairs; occurs as the AX2E shape class (bond angle < 120 degrees) in the trigonal planar arrangement and as the AX2E3 shape class (bond angle < 109.5 degrees) in the tetrahedral arrangement

Front 16

tetrahedral arrangement

Back 16

the geometric arrangement formed when four electron groups maximize their separation around a central atom; when al lfour groups are bonding groups, the molecular shape is tetrahedral (AX4; ideal bond angle 109.5 degrees)

Front 17

trigonal pyramidal shape

Back 17

a molecular shape (AX3E) caused by the presence of one lone pair in a tetrahedral arrangement

Front 18

trigonal bipyramidal arrangement

Back 18

the geometric arrangement formed when five electron groups maximize thier separation around a central atoms. when all five groups are bonding groups, the molecular shape is trigonal bipyramidal (AX5; ideal bond angles, axial-center-equatorial = 90 degrees and equatorial-center-equatorial = 120 degrees)

Front 19

equatorial group

Back 19

a group (or atom) that lies in the trigonal plance of a trigonal bipyramidal molecule, or a similar structural feature ina molecule

Front 20

axial group

Back 20

a group (or atom) that lies above or below the trigonal plane of a trigonal bipyramidal molecule, or a similar structural feature in a molecule

Front 21

seesaw shape

Back 21

a molecular shape caused by the presence of one equatorial lone pair in the trigonal bipyramidal arrangement (AX4E)

Front 22

T shape

Back 22

a molecular shape cuased by the presence of two equatorial lone pairs in a trigonal bipyramidal arrangement (AX3E2)

Front 23

octahedral arrangement

Back 23

the geometric arrangement obtained when six electron gropus maximize their separation around a central atom; when all six groups are bondign gropus, the molecular shape is octahedral (AX6; ideal bond angle = 90 degrees)

Front 24

square pyramidal shape

Back 24

a molecular shape (AX5E) caused by the presence of one lone pair in an octahedral arrangement

Front 25

square planar shape

Back 25

a molecular shape (AX4E32) caused by the presence of two axial lone pairs in an actahedral arrangement

Front 26

molecular polarity

Back 26

the overal distribution of electronic charge in a molecule, determined by its shape and bond polarities

Front 27

dipole moment

Back 27

a measure of molecular polarity; the magnitude of the partial charges on the ends of a molecule (in coulombs) times the distance between them (in meters)