Chapter 9: Chemical Bonds Flashcards Preview

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Flashcards in Chapter 9: Chemical Bonds Deck (106):
1

the ... electrons form bonds

valence

2

a lewis-dot symbol for an atom consists of the

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

3

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

low ionization energies

4

electrons are easily added to nonmetals because their

electron affinities are generally favorable

5

ionic bonding is the bonding that results from

electrostatic attraction between positively and negatively charged ions

6

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

equal the number gained to form the anions

7

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

sum of five simpler reactions

8

lattice energy is the energy required to separate

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

9

lattice enrgy is always

positive

10

E=

kQ1Q2/ r

11

k is a

constant

12

Q1 and Q2 are the

charges on the two particles

13

r is the

distance of separation in the compound

14

equation for E known as

coulomb's law

15

lattice energies are greatest for compounds made from

highly charged small ions

16

maximize ..., minimize ... to get the largest E

Q; r

17

ionic solids are stable because of

high lattice energies

18

ionic compounds are typically ... with ...

brittle solids; high melting points

19

covalent compounds are typically ... or ... at ...

liquids; gases; room temperature

20

when covalent compounds are solids, they are

low melting

21

a covalent bond is a bond that results from

atoms sharing electrons

22

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

minimum energy distance; nuclei of two bonded atoms

23

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

potential energy minimum; closer together

24

a covalent bond forms because two atoms sharing electrons are

lower in energy than the two isolated atoms

25

bonding pairs of electrons are

shared between two atoms

26

lone, or nonbonding, pairs of electrons are entirely

on one atom and are not shared

27

lewis structures show how valence electrons are

arranged among atoms in a molecule

28

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

noble gas electron configuration

29

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

numbers; types of bonds; geometry of the molecule

30

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

Surrounded by eight electrons

31

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

Two; two; three; one; four

32

Single bond;

Shares one electron pair

33

Double bond:

Shares two electron pairs

34

Triple bond:

Shares three electron pairs

35

Bond order: the number of

Electron pairs that are shared between two atoms

36

Skeleton structure shows which atoms are

Bonded to each other in a molecule

37

Central atom: an atom bonded to

Two or more other atoms

38

Nonpolar

Equal sharing of electrons

39

Polar

Unequal sharing of electrons

40

The polarity of a compound can be determined by

Placing the compound in an electric field

41

If a molecule is polar it will no longer have a

Random orientation In the electric field

42

dipole moment is a measure of the

unequal sharing of electrons

43

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

an electric field

44

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

polar covalent; δ; partial charges

45

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

shared electrons in a chemical bond

46

... is the most electronegative element

fluorine

47

electronegativity order of some elements

F>O>Cl=N

48

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

low; hgh

49

the polarity of a bond is proportional to the

difference in electronegativity between two covalently bonded atoms

50

electronegativities ... across a period and .. down a row

increase; decrease

51

nonpolar electronegativity diff.

up to 0.4

52

polar electronegativity diff

0.4-1.7

53

ionic electronegativity diff

>1.7

54

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

electrical conductance of the molten compound

55

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

divided equally between the bonded atoms

56

formal charge =

#v.e- - #lonepairelectrons - #bonds

57

lewis structures that show the .... formal chages are...

smallest; favored

58

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

same sign; much less favorable

59

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

more electronegative atoms; favored

60

formal charges of opposite sign are usually on

adjacent atoms

61

resonance structures: structures that differ only in the

distribution of valence electrons

62

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

written for a particular moleucle

63

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

shorter; stronger; longer; weaker

64

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

an average of all resonance structures

65

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

formal charges

66

four classes of molecules do not obey the octet rule:

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

67

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

2; 3; electron-deficient

68

electron-deficiency is typically seen with compounds containt

Be, B, Al

69

any molecule that has an odd number of valence electrons must

violate the octet rule

70

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

reactive; radicals

71

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

seven valence electrons

72

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

more than eight electrons

73

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

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

74

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

central atom as lone pairs

75

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

third; later; second period

76

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

d subshells; additional electrons

77

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

>= three; expanded valence shells

78

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

hydrogen atom; oxygen atom; (HO)mXOn

79

species with strong bonds are generally

stable

80

bond dissociation energy (D) is the energy required to

break one mole of bonds in a gaseous species

81

bond energies are always ...

endothermic

82

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

directly; averages

83

triple bonds are ... than double bonds which are ... than single bonds

stronger; stronger

84

triple and double bond lengths are ... than single bond lengths

shorter

85

ΔHreaction=

ΣDbondsbroken - ΣDbondsformed

86

breaking bonds always

requires energy

87

forming bonds always

releases energy

88

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

types and numbers of bonds broken and formed

89

in calculating, ΔHreaction .... are used

average bond energies

90

bond order=

#bonds/how many regions of bonding

91

for compounds, formal charges must add to

0

92

for polyatomic ions, formal charges should add to the

charge of the ion

93

(electronegativity) F=

4.0

94

(electronegativity) O=

3.5

95

(electronegativity) N=

3.0

96

(electronegativity) C=

2.5

97

(electronegativity) Cl=

3.0

98

(electronegativity) H=

2.1

99

(electronegativity) Br=

2.8

100

(electronegativity) I=

2.5

101

(electronegativity) S=

2.5

102

(electronegativity) P=

2.1

103

(electronegativity) Si=

1.8

104

(electronegativity) Al=

1.5

105

ionic compounds form from

metals and nonmetals;

106

nonmetal nonmetal compounds are usually

covalent bonds