General Chemistry- Bonding and Chemical Interactions Flashcards Preview

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Flashcards in General Chemistry- Bonding and Chemical Interactions Deck (180)
1

Most atoms can form what?

Molecules

2

What atoms are the exception to forming molecules?

The noble gases

3

How are the atoms in molecules held together?

Chemical bonds

4

What are chemical bonds?

Strong attractive forces

5

How are chemical bonds formed?

The interaction of the valence electrons of the combining atoms.

6

Compounds usually have similar or different chemical and physical properties as the elements that make them up?

Very different

7

For many molecules, the atoms combine based on what rule?

Octet rule

8

What is the octet rule?

An atom tends to bond with other atoms so that it has eight electrons in its outermost shell, thereby forming a stable electron configuration similar to that of the noble gases

9

Why is the octet rule on a rule of thumb?

There are more elements that can be exceptions to the rule than those that follow the rule.

10

Which elements are exceptions to the octet rule?

Hydrogen
Lithium
Beryllium
Boron
All elements in period 3 and greater

11

Which elements are stable with fewer than 8 electrons?

Hydrogen (2)
Helium (2)
Lithium (2)
Beryllium (4)
Boron (6)

12

Which elements are stable with an expanded octet?

Elements in period 3 or greater
Phosphorus (10)
Sulfar (12)
Chlorine (14)

13

What elements are another example of an exception to the octet rule?

An molecule with an odd number of valence electrons cannot distribute those electrons to give eight to each atom.

14

What is an example of an odd number molecule?

Nitric Oxide (NO)- (11)

15

What are the common elements that almost always abide by the octet rule?

Carbon
Nitrogen
Oxygen
Fluorine
Sodium
Magnesium

16

What are the two types of chemical bonds?

Ionic
Covalent

17

What occurs during ionic bonding?

One or more electrons from an atom with a low ionization energy, typically a metal, are transferred to an atom with a high electron affinity, typically a nonmetal.

18

What holds the ionic bonds togethere?

Electrostatic attraction between opposite charges

19

The electrostatic attraction in ionic bonds creates what?

Lattice structures consisting of repeating rows of cations and anions, rather than individual molecular bonds

20

What occurs in covalent bonding?

An electron pair is shared between two atoms, typically nonmetals, that have relatively similar values of electronegativity.

21

What determines the polarity in a covalent bond?

The degree to which the pair of electrons is shared equally or unequally between the two atoms

22

If the electron pair is shared equally in a covalent bond, it is _________?

Nonpolar

23

If the electron pair is shared unequally, the bond is ________________?

Polar

24

When is a bond called coordinate covalent?

If both of the shared electrons are contributed by only one of the two atoms

25

What is an example of nonpolar covalent bonding?

Diatomic fluorine

26

What do covalent compounds consist of?

Individually bonded molecules

27

Ionic bonds form between atoms that have ___________ ________.

Significantly different electronegativities

28

The atoms become what in ionic bonding?

cations and anions

29

The ionic bond is the result of ___________?

Electrostatic force of attraction between the opposite charges of these ions.

30

What are not shared in ionic bonds?

Electrons

31

What must occur before ionic bonding takes place?

The difference in elecctronegativity must be gre3ater than 1.7 on the pauling scale.

32

Ionic bonds are usually formed between what type of atoms?

Metals and nonmetals

33

How can you determine whether a compound will form an ionic bond, equation wise?

Difference in electronegativity values (/\EN)

34

What are three ionic bond examples?

Cesium chloride
Potassium Iodide
Sodium Fluoride

35

What are the common ionic compound characteristic physical properties?

High melting and boiling points
Dissolve in water and other polar solvents
In the molten or aqueous state good conductors of electricity
Form crystalline lattice with repeating positive and negative ions

36

Why does the formation of ionic compounds create such attractive force?

The attractive forces between the oppositely charged ions are maximized
Repulsive forces between ions of like charge are minimized

37

What type of atoms form covalent bonds?

Atoms with similar electronegativities

38

Why don't atoms with similar electronegativities form ions when bonded?

The energy required to form ions through the complete transfer of one or more electrons is greater than the energy that would be released upon the formation of an ionic bond. So it is energetically unfavorable to create ions.

39

What do covalent bonds contain?

Discrete molecular units with relatively weak intermolecular interactions.

40

Covalent bonds tend to have what?

Lower melting and boiling points

41

Covalent bonds are ________________ because ____________?

Poor conductors of electricity in the liquid state because they do not break down constituent ions.

42

What is it called when atoms share one, two, or three electrons?

Joined by
Single
Double or
Triple covalent bonds

43

What is the bond order?

The number of shared elecctron pairs between two atoms

44

What is the bond order for a single, double and triple bond?

Single: 1
Double: 2
Triple: 3

45

What are the three characteristics of a covalent bond?

Bond Length
Bond Energy
Polarity

46

What is bond length?

The average distance between the two nuclei of atoms in a bond.

47

As the nuber of electron pairs increases, bond length _______.

Decreases due to the two atoms being pulled closer together

48

What is bond energy?

The energy required to break a bond by separating its components into their isolated, gaseous atomic states.

49

The greather the number of pairs of electrons the ________ energy required to break them.

More

50

Which has a greater bond energy: single ro triple bond?

Triple

51

When does polarity occur?

When two atoms have a relative difference in electronegativities

52

Atoms with higher electronegativity get _______ share of __________.

Larger share of the electron density

53

What must be negotiated in a covalent bond?

Atoms must negotiate the degree to which the electron pairs are shared

54

What does a polar bond create?

A dipole

55

The ________ end of the dipole at the _________ and _____________ end at the __________.

Positive end of the dipole at the less electronegative atom and the negative end at the more electronegative atom

56

What is a non-polar covalent bond?

Atoms that have identical or nearly identical electronegativities and share electron pairs. They do so with equal distribution of the electrons.

57

There is no ________ in a non polar covalent bond?

Separation of charge across the bond

58

Only bond between _____________ will have exactly the same ___________.

Atoms of the same element willl have the exact same electronegativity

59

What are the seven common diatonic molecules?

H2
N2
O2
F2
Cl2
Br2
I2

60

When are bonds basically nonpolar?

Difference in electronegativity less than 0.5

61

Atoms that differ moderately in their electronegativities will result in ____________.

Polar covalent bonds

62

What is the range of difference in electronegatvities that result in polar covalent bonds?

0.5-1.7

63

The more electronegative the element the more ____________, taking on a ____________ charge.

Greater portion of the electron density taking on a partial negative charge.

64

The less electronegative the ___________, taking on a ________ charge.

Smaller portion of the electron density taking on a partial positive charge

65

How do you indicate the differece in charge?

An arrow crossed at its tail end and pointing toward the negative end.

66

What is the dipole moment?

A vector quantity give by the equation: p=qd

67

What do the letters represent in the dipole moment equation?

p: the dipole moment
q: magnitude of charge
d: the displacement vector separating the two partial charges

68

How is the dipole moment vector measured?

Debye units (Coulomb-meters)

69

What is a coordinate covalent bond?

Both of the shared electrons originated on the same atom.

70

What does it generally mean to have a coordinate covalent bond?

A lone pair of one atom attacked another atom with an unhybridized p-orbital to form a bond.

71

A distinction between where a coordinate bond comes from is only helpful, how?

For keeping track of the valence electrons and formal charges.

72

Where are coordinate covalent bonds typically found?

In Lewis acid-base reactions

73

What is a Lewis acid?

Any compound that will accept a lone pair of electrons

74

What is Lewis base?

Any compound that will donate a pair of electrons to form a covalent bond

75

What are bonding electrons?

The electrons involved in a covalent bond are in the valence shell

76

What are nonbonding electrons?

Electrons in the valence shell that are not involved in covalent bonds.

77

What are lone pairs?

Unshared electron pairs

78

Why are they called lone pairs?

because they are associated only with one atomic nucleus

79

Why was the Lewis structure developed?

To keep track of the bonded and nonbonded electron pairs

80

Is the valence electrons in a neutral atom the same as valence electrons in an atom in the Lewis structure?

No

81

Why is there a formal charage for an atom in a Lewis structure?

To note the difference in number of valence electrons in a neutral atom and a Lewis structure atom.

82

Can more than one Lewis strcutre be drawn for a molecule?

Yes

83

What happens if Lewis structures differ in their bond connectivity or arrangement?

Then the Lewis structures represent different possible compounds.

84

When does the Lewis strcture show different resonance forms?

If Lewis structures show the same bond connectivity and differ only in the arrangement of the electron pairs

85

Do Lewis structures respresent the actual geometry of a real compound?

No

86

How can you check the likelihood of each arrangement using the Lewis structure?

Checking the formal charges on the atoms in each arrangement.

87

How can you tell the stability of an arrangement based on the Lewis structure and formal charge?

The arrangement that minimizes the number and magnitude of formal charages is the most stable arrangement

88

What is another name for Lewis structure?

Lewis dot diagram

89

How is the Lewis structure drawn?

The chemical symbol of an element surrounded by dots, each representing one of the s or p valence electrons of the atom

90

Can a Lewis structure also show the valence electrons of molecules?

Yes

91

Which atom is the central atom in a Lewis structure?

The atom with the least electronegativity

92

Which atoms usually occupy a terminal position in a Lewis diagram?

Hydrogen
F
Cl
Br
I

93

Which atom ALWAYS occupies a terminal position?

Hydrogen

94

What are the steps for drawing a Lewis structure?

Draw skeletal structure
Count valence electrons
Draw single bond
Draw remaining valence electrons of attached atoms
Complete octet of central atom by making multiple bonds if need be.

95

How can you count the valence electrons of a molecule?

Sum of the valence electrons of all atoms present

96

How do you draw electrons in a Lewis diagram?

Dots

97

How are bonded electron pairs drawn in a Lewis structure?

A line: Which represents a pair of electrons

98

How do you determine if a Lewis structure is a representation of an actual arrangement of atoms in a compound?

One must calculate the formal charge of each atom.

99

What should be assumed when calculating formal charage in a Lewis structure?

Assume that each electron pair is split evently betweeen the two nuclei in the bond.

100

What is the equation to calculate formal charge?

Formal Charage=V-(Nnonbonding)- 1/2 (Nbonding)

101

What do the letters represent in the equation to calculate formal charge?

V: normal number of electrons in the atom's valence shell
(Nnonbonding): # of nonbonding electrons
(Nbonding): # of bonding electrons

102

What is the difference between formal charge and oxidation number?

Formal charge underestimates the effect of electronegativity differences, wheras oxidation numbers overestimate the effect of electronegativity differences.

103

What is the resounance structures?

Two or more Lewis structures that demonstrate the same arrangement of atoms but that differ in the specific placement of the electrons

104

How are resonance structures represented?

With a Double-headed arrow between them

105

What is resonance hybrid?

The actual structure of the compound

106

What contributes more to the resonance hybrid?

The more stable the structure, the more it contributes to the character of the resonance hybrid.

107

What are the guidelines for determining the stability of resonance structures?

A Lewis structure with small or no formal charges is preferred over a Lewis structure with large formal charges
A Lewis structure with less separation between opposite charages is preferred over a Lewis structure with a large separation of opposite charges
A Lewist structure in which negative formal charges are placed on more electronegative atoms is more stable than one in which the negative formal charges are placed on less electronegative atoms

108

On test day, what should not be discounted in regards to Lewis structures/

Lewis structure with a central atom that has more than four bonds.

109

What is the valence shell electron pair repulsion theory?

VSEPR

110

What does VSEPR do?

Uses Lewis dot structures to predict the molecular geometry of covalently bonded molecules.

111

What does the VSEPR theory state?

The three-dimensional arrangement of atoms surrounding a central atom is determined by the repulsions between bonding and nonbonding electron pairs in the valence shell of the central atom.

112

What are the steps for predicting the geometrical structure of a molecule?

Draw the Lewis dot structure of the molecule.
Count the total number of bonding and nonbonding electron pairs in the valence shell of the central atom.
Arrange the electron pairs around the central atom so that they are as far apart as possible.

113

What are the 5 most common shapes of configuration of molecules that do not have charge or lone pair of electrons around the central atom according to the VSEPR theory?

Linear
Tigonal Planar
Tetrahedral
Trigonal Bipyramidal
Octahedral
p.88

114

What are the angles of the 5 most common shapes of configuration of molecules that do not have charge or lone pair of electrons around the central atom according to the VSEPR theory?

Linear: 180 degrees
Tigonal Planar: 120 degrees
Tetrahedral: 109.5 degrees
Trigonal bipyramidal: 90 degrees, 120 degrees, 180 degrees
Octahedral: 90 degrees, 180 degrees
p,88

115

What are the regions of the electron density of the 5 most common shapes of configuration of molecules that do not have charge or lone pair of electrons around the central atom according to the VSEPR theory?

Linear: 2
Trigonal planar: 3
Tetrahedral: 4
Trigonal bipyramidal: 5
Octahedral: 6
p.88

116

What are examples of molecules that follow the 5 most common shapes of configuration of molecules that do not have charge or lone pair of electrons around the central atom according to the VSEPR theory?

Linear: BeCl2
Trigonal Planar: BH3
Tetrahedral: CH4
Trigonal Bipyramidal: PCL5
Octahedral: SF6
p.88

117

What is the difference between electronic geometry and molecular geometry?

Electronic geometry describes the spatial arrangement of all pairs of electrons around the central atom, including both the bonding and the lone pairs.
Molecular geometry describes the spatial arrangement of only the bonding pairs of electrons.

118

What is one important implication of electronic geometry?

The determination of the ideal bond angle.

119

What will the MCAT primarily focus on: molecular geometry or electronic geometry?

Molecular geometry

120

Why is the ideal bond angle important in electronic geometry?

Nonbonding pairs are able exert more repulsion than bonding pairs because these electrons reside closer to the nucleus.

121

What is molecular dipole?

An overall separation of charge across the molecule

122

Does the presence of bond dipoles result in a molecular dipole?

No the presence of bond dipoles does not necessarily result in a molecular dipole

123

How do you determine molecular dipole?

The molecular geometry and the vector addition of the bond dipoles based upon the molecular geometry.

124

Does a compound with nonpolar bond ever have a polar molecular dipole?

No, it is always nonpolar

125

Does a compound with polar bond ever have a polar molecular dipole?

May be polar or nonpolar

126

What determines molecular dipole in a molecule with polar bonds?

The spatial orientation of the polar bonds in the molecule

127

What type of geometry results in a nonpolar compound?

Molecular geometry such that the bond dipole moments cancel each other out, then the result is a nonpolar compound

128

What type of geometry results in a net dipole moment?

Molecular geometry is arranged such that the bond dipoles do not cancel each other out, the molecule will have a net dipole moment and will therefore be polar

129

What do the 4 quantum nummbers describe?

The energy and position of an electrong in an atom.

130

What does the principle quantum number indicate?

The average energy level of the shell

131

What does the azimuthal quantum number describe?

The subshells within each principal energy level

132

What is the shape of the s subshell which has one orbital?

Spherical

133

What is the shape of the p subhsell, and what axes are they on? What angles do they make with each other?

Barbells along the x, y, z axes at right angles to each other

134

When two atoms bond to form a compound, what interaction occurs?

The atomic orbitals interact to form a molecular orbital

135

What does the molecuar oribtal describe?

The probability of finding the bonding electrons in a given space.

136

How are molecular orbitals obtained?

Combining the wave functions of the atomic orbitals.

137

Qualitatively, how are molecular orbitals described?

The overlap of two atomic orbitals describes this molecular orbital

138

How is a bonding orbital formed?

If the wavelength signs of the two atomic orbitals are the same

139

How is an antibonding orbital formed?

If the wavelength signs of the two atomic orbitals are different

140

How many patterns of overlap are observed in the formation of molecular bonds?

Two

141

What results in a sigma bond?

When orbitals overlap head-to-head

142

What do sigma bonds allow? Why?

For free rotation about their axes because the electron density of the bonding orbital is a single linear accumulation between the atomic nuclei.

143

What results in a pi bond formation?

When the orbitals overlap in such a way that there are two parallel electron cloud densities.

144

Pi bonds do not allow for what? Why?

For free rotation because the electrong densities of the oribitals are parallel and cannot be twisted in such a way that allows continuous overlapping of the clouds of electron densities.

145

The strength of ________ can impact _________ such as ________ and ____________.

These intermolecular forces can impact certain physical properties, such as meling and boiling points.

146

What is the weakest intermolecular interation?

Dispersion forces

147

What is another name for dispersion forces?

London forces

148

Which intermolecular interaction has intermediate strength?

Dipole-Dipole interactions

149

Which intermolecular interation is the strongest?

Hydrogen bond

150

Why is the hydrogen bond a misnomer?

There is no actual sharing or transfer of electrons

151

What do atoms and compounds participate in?

Weak electrostatic interactions.

152

Even the strongest intermolecular force, the ________, is not as strong as ___________.

The hydrogen bond, is not as strong as the covalent bond.

153

WHat percentage of strength does a hydrogen bond have compared to a covalent bond?

10 percent

154

How much energy i required to overcome an electrostatic interaction?

Small or moderate amounts of energy

155

In a given moment, bonding electrons in nonpolar covalent bond, may be what?

unequally distributed between the two atoms

156

What is the result of bonding electrons in nonpolar covalent bonds with unequally distributed electron cloud?

A rapid polarization and counterpolarization of the electrong cloud and the formation of short-lived dipole moments.

157

The rapid polarization and counterpolariation of covalent bonds ineracts with what? Causing what?

The electron clouds of neighboring compounds, inducing the formation of more dipoles

158

What is the name of the attractive interactions of these short-lived and rapidly shifting dipoles?

London Dispersion forces

159

The London dispersion force is a type of what force?

Van der Waals force

160

London dispersion forces do not what? Therfore are what?

Do not extend over long distance and therefore are significant only when molecules are in close proximity

161

The strength of a London dispersion force depends on what?

The degree and ease by which the molecules can be polarized

162

Which type of molecules are easily polarized: Small or large molecules? Thus they have greater what?

Large molecules are more easily polarizable and thus possess greater dispersion forces

163

Which force is the only force that can cause noble gases to interact/liquify at any temperature?

Dispersion forces

164

Polar molecules orient themselves how, when they interact?

The oppositely charged ends of the respective molecular dipoles are closest to each other

165

What type of force is formed between two polar molecules that make up a compound?

An attractive electrostatic force

166

The dipole-dipole interaction is indicated how, when notating?

The attractive force is denoted by dashed lines in most molecular notations and indicates a temporary bonding interaction

167

Dipole-dipole interactions are present in what phases?

Solid and liquid phases

168

Why are Dipole-Dipole interactions not seen in the gas phase?

The significantly increased distance between gas particles

169

What is a result of dipole-dipole interactions compared to non-polar species of comparable molecular weight?

Polar species tend to have higher melting and boiling points than nonpolar species of comparable molecular weight due to these interactions

170

What is the similarty and difference of Dipole-dipole forces and Lond dispersion forces.

Both are electrostatic forces between opposite partial charges,
The difference is only in the transience or permanence of the molecular dipole

171

What is a hydrogen bond?

A specific, usually strong form of dipole-dipole interaction that may be intra-or intermolecular.

172

Hydrogen bonds are not _________, because __________.

Actually bonds, there is no sharing or transfer of electrons between atoms

173

What are the three highly electronegative atoms?

Nitrogen
Oxygen
Fluorine

174

When hydrogen is bonded to a highly electronegative atom, it carries only ___________.

A small amount of the electron density in the covalent bond.

175

The hydrogen atom acts as what in a hydrogen bond?

A naked proton

176

Substances that display hydrogen bonding tend to have ___________ compared to _______________.

Unusually high boiling points compared to compounds of similar molecular weights that do not exhibit hydrogen bonding.

177

The high boiling point in substances with hydrogen bonds derives from what?

The energy required to break the hydrogen bonds.

178

Hydrogen bonding is particularly important in the behavior of what?

Water
Alcohols
Amines
Carboxylic Acids

179

What has different regions that are stabilized by hydrogen bonding?

Many biochemical molecules, such as nucleotides

180

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