Chapter 10: Molecular Structure and Bonding Theories Flashcards

1
Q

the arrangement of the atoms in a molecule has a strong influence on its

A

physical properties and chemical reactivity

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2
Q

the valence-shell electron-pair repulsion (VSEPR) model predicts the shapes of most molecules from their

A

Lewis structures

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3
Q

the main premise of VSEPR model is that the electron pairs about an atom

A

repel each other

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4
Q

VSEPR Rule 1: a molecule hs a shape that …..

A

minimizes eletrostatic repulsions between valence-shell electron pairs

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5
Q

minimum repulsion results when the electron pairs are as

A

far apart as possible

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6
Q

the VSEPR model predicts the shape around

A

each central atom

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7
Q

steric number =

A

(number of lone pairs on central atom) + (number of atoms bonded to central atom)

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8
Q

the steric number is used to determine the

A

bonded-atom lone-pair arrangement

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9
Q

the BALPA is the shame that maximizes the distances between

A

regions of electron density about a central atom

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10
Q

bond angles for linear

A

180

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11
Q

bond angles for trigonal planar

A

120

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12
Q

bond angles for tetrahedral

A

109.5

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13
Q

bond angles for trigonal bipyramidal

A

90 and 120

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14
Q

bond angles for octahedral

A

90 and 90

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15
Q

SN: 2, balpa:

A

linear

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16
Q

SN: 3, BALPA:

A

trigonal planar

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17
Q

SN: 4, BALPA:

A

tetrahedral

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18
Q

SN: 5, BALPA:

A

trigonal bipyramidal

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19
Q

SN: 6, BALPA:

A

octahedral

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20
Q

two positions for molecular shapes:

A

axial and equatorial

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21
Q

axial atoms have different … from equatorial ones

A

environments

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22
Q

when central atoms have lone pairs, the molecular shape is not the same as the

A

bonded-atom lone-pair arrangement

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23
Q

the molecular shape is the geometric

A

arrangement of the atoms in a species

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24
Q

the lone pairs influence the molecular shape but are …, because there are no atoms at the …

A

not part of it; locations of the lone pairs

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25
Q

each type of electron pair exerts a different

A

repulsion on other electron pairs

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26
Q

VSEPR Rule 2: forces between electron pairs vary as

A

lone-pair-lone-pair repulsion>lone-pair-bonding-pair repulsion>bonding-pair-bonding-pair repulsion

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27
Q

in a trigonal bipyramidal BALPA, the structure that minimizes the number of 90 degree lone pair interactions is favored-

A

lone pairs always go to the equatorial position

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28
Q

for molecules with more than one central atom, the geometry about each atom is assigned by applying the VSEPR model to each

A

central atom individually

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29
Q

the VSEPR model does not predict how the geometry around one central atom will be oriented with respect to

A

others in the moleule

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30
Q

polar molecules will orient to maximie

A

electrostatic attractions

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31
Q

the degree of polarity is measured by a

A

dipole moment

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32
Q

the dipole moment is the magnitude of the separated charges times the

A

distance between them

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33
Q

the … between bonded atoms is used to predict the polarity of each bond, known as the …

A

difference in electronegativity; bond dipole

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34
Q

the dipole moment of the molecule is the

A

vector sum of the individual bond dipoles

35
Q

molecules with lone pairs of electrons on a central atom generally are

A

polar

36
Q

a molecule with polar bonds is nonpolar if its geometry causes the

A

bond polarities to sum to zero

37
Q

molecules are nonpolar when there are no … on the central atom and all of the atoms bonded to the central atom are …

A

lone pairs; identical

38
Q

valence bond theory describes covalent bonds as being fromed by atoms sharing valence electrons in

A

overlapping valence orbitals

39
Q

(valence bond theory) the bonding is based on the … available to make bonds and the …. that the atoms provide for bonding

A

orbitals; number of valence electrons

40
Q

hybrid orbitals are orbitals obtained by

A

mixing two or more atomic orbitals of the same central atom

41
Q

the new hybrid orbitals have different … and … properties from the orbitals used in constructing them

A

shapes; directional

42
Q

the energy and directional characteristics of the new hybrid orbitals are decided by the … and … of atomic orbitals used in the mixing

A

type; number

43
Q

1 s orbital + 1 p orbital forms

A

two sp hybrid orbitals

44
Q

the sp hybrid orbitals describe the bonding on central atoms that have

A

180 degree bond angles

45
Q

the steric number of 2 indicates … hybrid orbitals

A

sp

46
Q

1 s orbital + 2 p orbitals forms

A

3 sp^2 hybrid orbitals

47
Q

for sp2 hybrid orbitals, … remains unchanged

A

one p orbital

48
Q

the sp2 hybrid orbitals describe the bonding on atoms that have … and a steric number of ..

A

120 degree bond angles; 3

49
Q

1 s orbital + 3 porbitals forms

A

4 sp^3 hybrid orbitals

50
Q

the sp3 hybrid orbitals describe the bonding on central atoms that have approximately …. and a steric number of ..

A

109-degree bond angles; 4

51
Q

for molecules that have central atoms with steric numbers of 5 or 6, more than … are needed to make the hybrid orbitals

A

four atomic orbitals

52
Q

the additional orbitals are taken from the

A

d subshell

53
Q

1 d orbital + 1 s orbital + 3 p orbitals forms

A

5 sp^3d hybrid orbitals

54
Q

2 d orbitals + 1s orbital + 3 p orbitals

A

six sp^3d^2 hybrid orbitals

55
Q

the steric number and number of hybrid orbitals are

A

equivalent

56
Q

sigma bonds exist int he region

A

directly between two bonded atoms

57
Q

in a sigma bond, the shared pair of electrons is symmetric about th eline

A

joining the two nuclei of the bonded atoms

58
Q

all single bonds are

A

sigma bonds

59
Q

sigma bonds form from the overlap of … orbitals or hybrid orbitals oriented …

A

s or p; along the bond

60
Q

all hybrid orbitals make only

A

sigma bonds

61
Q

pi bonds exist in the region … between two bonded atoms

A

above and below a line drawn

62
Q

double bonds have .. sigma bond and … pi bond

A

1; 1

63
Q

triple bonds have .. sigma bond and … pi bond

A

1; 2

64
Q

isomers are compounds with the same … but different …

A

molecular formula; structures

65
Q

when double bonds are formed between two carbon atoms, the potential for … isomerism arises due to lack of … around double bonds

A

cis-trans; rotation

66
Q

cis-trans isomerism is observed only if each carbon atom has

A

2 different substitutents attached

67
Q

pi bonds contribute to the … model of electrons in bonding, and help explain ..

A

delocalized; resonance

68
Q

electron density from pi bonds can be distributed … all around the ring, above and below the plane

A

symmetrically

69
Q

molecular orbital theory is a model that combines atomic orbitals to form new orbitals that are shared over the

A

entire molecule rather than between two atoms

70
Q

a molecular orbital is a … of an electron in a molecule

A

wave function

71
Q

the number of molecular orbitals formed must equal the number of

A

atomic orbitals used to make them

72
Q

these wave functions can be added to generate … or they can be subtracted to generate …

A

bonding orbitals; anti-bonding orbitals

73
Q

bonding orbitals concentrate electron density

A

between atoms

74
Q

anti-bonding orbitals reduce the

A

electron density between atoms

75
Q

bonding molecular orbitals are … and antibonding molecular orbitals are … than the atomic orbitals that are combined

A

more stable; less stable

76
Q

moleuclar orbital theory allows us to calculate bond order (…) and the number of unpaired electrons (…)

A

measure of stability; paramagnetism

77
Q

according to molecular orbital theory, bond order is :

A

1/2(# e- in bonding orbitals - #e- in anti-bonding orbitals)

78
Q

a homonuclear diatomic molecule contains

A

two atoms of the same element

79
Q

heteronuclear diatomic molecules contain one atom of each of

A

two different elements t

80
Q

the molecular orbital diagrams are close to those for homonuclear diatomic molecules when the valence energies for each atom are

A

fairly close in energy

81
Q

delocalized molecular orbitals are: orbitals in which an electron in a molecule is

A

spread over more than two atoms

82
Q

cis: same substituents

A

parallel

83
Q

trans: substitutents are

A

opposite to each other