Chapter 9: Chemical Bonds Flashcards

1
Q

the … electrons form bonds

A

valence

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2
Q

a lewis-dot symbol for an atom consists of the

A

symbol for the element surrounded by dots, one for each valence electron

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3
Q

electrons are usually removed from groups 1 and 2 because they have

A

low ionization energies

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4
Q

electrons are easily added to nonmetals because their

A

electron affinities are generally favorable

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5
Q

ionic bonding is the bonding that results from

A

electrostatic attraction between positively and negatively charged ions

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6
Q

when an ionic coompound forms, the number of electrons lost in forming the cations must

A

equal the number gained to form the anions

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7
Q

born-haber cycle: a process in which the formation of an ionic compond is shown as the

A

sum of five simpler reactions

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8
Q

lattice energy is the energy required to separate

A

one mole of an ionic crystalline solid into the isolated gaseous ions

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9
Q

lattice enrgy is always

A

positive

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10
Q

E=

A

kQ1Q2/ r

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11
Q

k is a

A

constant

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12
Q

Q1 and Q2 are the

A

charges on the two particles

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13
Q

r is the

A

distance of separation in the compound

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14
Q

equation for E known as

A

coulomb’s law

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15
Q

lattice energies are greatest for compounds made from

A

highly charged small ions

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16
Q

maximize …, minimize … to get the largest E

A

Q; r

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17
Q

ionic solids are stable because of

A

high lattice energies

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18
Q

ionic compounds are typically … with …

A

brittle solids; high melting points

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19
Q

covalent compounds are typically … or … at …

A

liquids; gases; room temperature

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20
Q

when covalent compounds are solids, they are

A

low melting

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21
Q

a covalent bond is a bond that results from

A

atoms sharing electrons

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22
Q

the bond length is the … between the … in a molecule

A

minimum energy distance; nuclei of two bonded atoms

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23
Q

bond length is determined by a … observed as the two atoms move ..

A

potential energy minimum; closer together

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24
Q

a covalent bond forms because two atoms sharing electrons are

A

lower in energy than the two isolated atoms

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25
Q

bonding pairs of electrons are

A

shared between two atoms

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26
Q

lone, or nonbonding, pairs of electrons are entirely

A

on one atom and are not shared

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27
Q

lewis structures show how valence electrons are

A

arranged among atoms in a molecule

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28
Q

lewis structures reflect the central idea that stability of a compound relates to

A

noble gas electron configuration

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29
Q

lewis structures show the .. and …, not the …

A

numbers; types of bonds; geometry of the molecule

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30
Q

The octet rule states that each atom in a molecule shares electrons until it is

A

Surrounded by eight electrons

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31
Q

In most Lewis structures oxygen makes … bonds and has … lone electrons; nitrogen makes … bonds and has … lone pair; carbon makes … bonds

A

Two; two; three; one; four

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32
Q

Single bond;

A

Shares one electron pair

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33
Q

Double bond:

A

Shares two electron pairs

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34
Q

Triple bond:

A

Shares three electron pairs

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35
Q

Bond order: the number of

A

Electron pairs that are shared between two atoms

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36
Q

Skeleton structure shows which atoms are

A

Bonded to each other in a molecule

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37
Q

Central atom: an atom bonded to

A

Two or more other atoms

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38
Q

Nonpolar

A

Equal sharing of electrons

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39
Q

Polar

A

Unequal sharing of electrons

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40
Q

The polarity of a compound can be determined by

A

Placing the compound in an electric field

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41
Q

If a molecule is polar it will no longer have a

A

Random orientation In the electric field

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42
Q

dipole moment is a measure of the

A

unequal sharing of electrons

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43
Q

the dipole moment of a compound can be determined by placing the compound in

A

an electric field

44
Q

the unequal sharing leads to a … bond that is indicated with the symbol … followed by a sign to show …

A

polar covalent; δ; partial charges

45
Q

electronegativity is the measure of the ability of an atom to attract the

A

shared electrons in a chemical bond

46
Q

… is the most electronegative element

A

fluorine

47
Q

electronegativity order of some elements

A

F>O>Cl=N

48
Q

elements with low ionization energies have … electronegativities, and elements with high ionization eneries have … electronegativities

A

low; hgh

49
Q

the polarity of a bond is proportional to the

A

difference in electronegativity between two covalently bonded atoms

50
Q

electronegativities … across a period and .. down a row

A

increase; decrease

51
Q

nonpolar electronegativity diff.

A

up to 0.4

52
Q

polar electronegativity diff

A

0.4-1.7

53
Q

ionic electronegativity diff

A

> 1.7

54
Q

but to truly identify a substance as ionic, you must assess the

A

electrical conductance of the molten compound

55
Q

formal charge is a charge assigned to atoms in lewis structures by assuming the shared electrons are

A

divided equally between the bonded atoms

56
Q

formal charge =

A

v.e- - #lonepairelectrons - #bonds

57
Q

lewis structures that show the …. formal chages are…

A

smallest; favored

58
Q

lewis structures that have adjacent atoms with formal charges of the …. are …

A

same sign; much less favorable

59
Q

lewis structures that place negative formal charges on the … are…

A

more electronegative atoms; favored

60
Q

formal charges of opposite sign are usually on

A

adjacent atoms

61
Q

resonance structures: structures that differ only in the

A

distribution of valence electrons

62
Q

resonance is invoked when more than one valid Lewis structure can be

A

written for a particular moleucle

63
Q

resonance bonds are … and …. than single bonds and … and …. than double bonds

A

shorter; stronger; longer; weaker

64
Q

no resonance structure is correct by itself, the correct structure is

A

an average of all resonance structures

65
Q

sometimes resonance structures are not equivalent, so … are used to determine which structure is favored

A

formal charges

66
Q

four classes of molecules do not obey the octet rule:

A

electron-deficient; odd-electron; expanded valence shell; oxides & oxyacids

67
Q

central atoms from groups … and … do not have enough valence electrons to complete an octet and are thus …

A

2; 3; electron-deficient

68
Q

electron-deficiency is typically seen with compounds containt

A

Be, B, Al

69
Q

any molecule that has an odd number of valence electrons must

A

violate the octet rule

70
Q

odd-electron molecules are highly …, and are called …

A

reactive; radicals

71
Q

in the lewis structure of a molecule that contains an odd number of electrons, one atom has only

A

seven valence electrons

72
Q

expanded valence shell molecules have … about an atom in a lewis structure

A

more than eight electrons

73
Q

a large class of expanded valence shell compounds have the general formula …, where Y= …

A

YFn; P, S, Cl, As, Se, Br, Te, I, or Xe

74
Q

when more electrons are available than are needed to satisfy the octet rule for all atoms present, place the extra electrons around the

A

central atom as lone pairs

75
Q

the octet rule can be exceeded for elements in … and … periods, but not for elements in the

A

third; later; second period

76
Q

the octet rule is based on the idea that the valence s and p subshells can hold eight electrons, but atoms in the third and later periodshave …tat can hold ….,exceeding an octet

A

d subshells; additional electrons

77
Q

oxides and oxyacids of p-block elements in periods …. typically have …

A

> = three; expanded valence shells

78
Q

oxyacids have at least one … attached to an …. and has the general formula

A

hydrogen atom; oxygen atom; (HO)mXOn

79
Q

species with strong bonds are generally

A

stable

80
Q

bond dissociation energy (D) is the energy required to

A

break one mole of bonds in a gaseous species

81
Q

bond energies are always …

A

endothermic

82
Q

bond energies for diatomic molecules are measured …., other bond energies are …

A

directly; averages

83
Q

triple bonds are … than double bonds which are … than single bonds

A

stronger; stronger

84
Q

triple and double bond lengths are … than single bond lengths

A

shorter

85
Q

ΔHreaction=

A

ΣDbondsbroken - ΣDbondsformed

86
Q

breaking bonds always

A

requires energy

87
Q

forming bonds always

A

releases energy

88
Q

to calculate ΔHreaction, the lewis structures need to be written to determine the

A

types and numbers of bonds broken and formed

89
Q

in calculating, ΔHreaction …. are used

A

average bond energies

90
Q

bond order=

A

bonds/how many regions of bonding

91
Q

for compounds, formal charges must add to

A

0

92
Q

for polyatomic ions, formal charges should add to the

A

charge of the ion

93
Q

(electronegativity) F=

A

4.0

94
Q

(electronegativity) O=

A

3.5

95
Q

(electronegativity) N=

A

3.0

96
Q

(electronegativity) C=

A

2.5

97
Q

(electronegativity) Cl=

A

3.0

98
Q

(electronegativity) H=

A

2.1

99
Q

(electronegativity) Br=

A

2.8

100
Q

(electronegativity) I=

A

2.5

101
Q

(electronegativity) S=

A

2.5

102
Q

(electronegativity) P=

A

2.1

103
Q

(electronegativity) Si=

A

1.8

104
Q

(electronegativity) Al=

A

1.5

105
Q

ionic compounds form from

A

metals and nonmetals;

106
Q

nonmetal nonmetal compounds are usually

A

covalent bonds