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college chem 117 > midterm exam 2 > Flashcards

midterm exam 2 Flashcards

1
Q

what does coulombs law describe the attraction between

A

2 charged particles

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2
Q

whats the formula for coulombs law

A

F=kQ1Q2/d^2

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3
Q

what does Q1 and Q2 represent in coulombs law, what does d represent

A

magnitude of the two charges, distance between their centers

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4
Q

what does a negative value from coulombs law represent? a positive?

A

negative is 2 particles attracted and positive is two particles repelled

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5
Q

what cancels some of the attraction to the nucleus

A

electron-electron repulsion

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6
Q

Valance e- are _____/______ from the nuclear charge by the ____ e-

A

screened/shielded, core

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7
Q

which formula do we use to account for screening

A

effective nuclear charge

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8
Q

what is the formula for effective nuclear charge

A

Zeff = Z-S

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9
Q

what does Z mean in the effective nuclear charge formula? the S?

A

Z is the atomic number/ the entire positive nuclear charge, S is a positive screening constant

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10
Q

can Zeff ever be larger than the atomic number? Why?

A

No, bc S is always a positive number

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11
Q

what is the simplest way to define S (using sum)

A

the sum of all electrons in orbitals of lower principal quantum number than the e- for which you are interested in determining the shielding

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12
Q

what is the periodic trend for Zeff

A

effective nuclear charge INCREASES from left to right across the period

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13
Q

does Zeff have a period trend up or down a group?

A

No it remains the same

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14
Q

what is the most important period trend/property

A

Zeff

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15
Q

what is explained by knowing that elements I the same group have very similar effective nuclear charge for valance e-

A

why elements in the same group have shared chemistry

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16
Q

how is atomic size defined

A

the distances between the nuclei of atoms

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17
Q

what is the metallic radius

A

half the distance between 2 identical adjacent nuclei in a solid metal

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18
Q

what is the covalent radius

A

half the distance between 2 adjacent nuclei connected by a covalent chemical bond

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19
Q

what is the Van Der Waals radius

A

half the distance between the nuclei of atoms that are touching but not bonding

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20
Q

what is another name that pertains to the covalent and metallic radius, but not to the Van Der Waals

A

bonding atomic radius

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21
Q

what is the periodic trend for bonding atomic radius

A

increases from top to bottom, decreases from left to right

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22
Q

which corner of a periodic table has the largest bonding atomic radius

A

bottom left

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23
Q

why do elements to the right of a period have a smaller bonding atomic radius than elements on the left

A

since as we move to the right of the period, the Zeff is higher, so there is a higher to the nucleus and the e- is held closer making the bonding atomic radius smaller

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24
Q

what are the cations and anions representing from a periodic table

A

only the most common tendency when an element is acting as an ion

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25
Q

what does forming an ion require

A

energy

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26
Q

do all elements always form ions

A

NOOOOO

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27
Q

are atomic radii and ionic radii the same size

A

no, they differ

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28
Q

is the radius of Na or Na+ larger

A

Na

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29
Q

is the radius of Cl or Cl- larger

A

Cl-

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30
Q

in general ____ are smaller than the atoms they are derived from and _____ are larger than the atom they are derived from

A

cations, anions

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31
Q

does ionic radius increase up or down a group

A

down

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32
Q

what is an isoelectronic series

A

a collection of atoms or ions that all have the same number of e-

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33
Q

does ionic radius increase or decrease from left to right in a period

A

decrease

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34
Q

which ion is expected to be larger P^3- or S^2-, why?

A

P^3- because the Zeff of Sulfur is stronger so the e- will be pulled closer in S than in P

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35
Q

which ion is expected to be smaller, Cl- or K+, why?

A

K+, cations are always smaller than anions if isoelectronic

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36
Q

what is ionization energy

A

the minimum energy needed to remove an electron from an atom in a gas phase

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37
Q

whats the formula for first ionization energy

A

X(g) yields X+(g) + e-(g)

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38
Q

Since removing an electron requires energy, is IE positive or negative value?

A

positive

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39
Q

what is 1 eV equal to in J

A

1.602 x 10^-19 J

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40
Q

what is the periodic trend of first ionization energy

A

increases from left to right across a period, decreases from top to bottom within a group

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41
Q

which corner would have the highest first ionization energy

A

top right

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42
Q

how are Zeff and ionization energy related

A

parallel, as Zeff increases, ionization energy increases

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43
Q

how are atomic radius and ionization energy related, why?

A

inversely, as atomic radius increases, the ionization energy decreases because the further from the nucleus an e- is, the less tightly its held

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44
Q

what is the second ionization energy

A

the energy required to remove an e- from an ion with a +1 charge

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45
Q

whats the formula for second ionization energy

A

X+(g) yields X2+(g) + e-(g)

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46
Q

which is ALWAYS larger, the first or second ionization energy

A

the second

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47
Q

what is a cause for a drastic increase in ionization energy

A

when we have to take an e- from the core

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48
Q

why is the first ionization energy of boron slightly less than that of beryllium

A

an exception, the energy of the e- increases slightly upon occupation of the p orbitals

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49
Q

why is the first ionization energy of Oxygen slightly less than that of Nitrogen

A

an exception, the repulsion between 2 electrons within the same 2px orbital makes it slightly easier to remove an e-

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50
Q

what is pairing energy

A

repulsion between e- in the same atomic orbital

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51
Q

what is electron affinity

A

the energy released when an atom in the gas phase accepts an e-

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52
Q

whats the formula for e- affinity

A

X(g) + e-(g) yields X-(g)

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53
Q

is ionization energy endothermic or exothermic? electron affinity?

A

ionization energy is endothermic, electron affinity is exothermic

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54
Q

what does a negative EA correspond to

A

a release of energy during the reaction

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55
Q

does exothermic gain or release energy

A

releases

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56
Q

the more _____ the EA, the reaction is more favorable

A

negative

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57
Q

in ionization energy, large values correspond to reactions that require a substantial _____ of energy

A

input

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58
Q

how are the first ionization energy and the electron affinity of an F- ion related

A

the energies are the same in magnitude, the amount of energy released when gaining an e- is equal to the amount of energy needed to remove an e-

59
Q

why do bonds form

A

because it lowers the energy

60
Q

does EA have a trend from top to bottom within a group

A

NOOO

61
Q

what is EA periodic trend

A

it generally increases from left to right across a period until the noble gasses which are practically 0

62
Q

why is the EA of nitrogen practically 0

A

an exception, if we add an e- to Nitrogen, it has to pair to an e- in the 2px orbital creation a repulsion which needs energy

63
Q

why does Be have an EA of practically o

A

an exception, if we add an e- to Be, it has to go from the s orbital to the p orbital which is higher in energy

64
Q

what are the trends of EA and IE driven by

A

Zeff and ground state electron configurations

65
Q

look over chart on last page of Geraldine notes

A

OKAYYY

66
Q

are e- in bonds more or less stable than e- in isolated atoms of the same element

A

more

67
Q

what is the formula for bond order

A

BO = (# of bonding electrons - # of anti-bonding electrons)/2

68
Q

do core e- have high or low energy

A

low

69
Q

why don’t core atomic orbitals overlap with orbitals of other atoms

A

they’re too small and too low in energy

70
Q

molecular orbitals are formed between atomic orbitals in the valance shell that have _____ energy and sizes

A

similar

71
Q

how do the e- fill the orbitals of a MO diagram

A

increaseing energy, from bottom to top

72
Q

electrons that are ______ in energy than when they are in the atomic orbitals are bonding

A

lower

73
Q

electrons that are ______ in energy than when they are in the atomic orbitals are antibonding

A

higher

74
Q

what is the general description of bond order

A

how many e- are in bonding orbitals relative to antibonding orbitals

75
Q

of molecular orbitals formed is _____ the number of atomic orbitals used to form then

A

the same as

76
Q

what are the 2 ways p orbitals overlap

A

side to side, end to end

77
Q

where are you most likely to find an e- in a bonding orbital

A

in between the two nucleii

78
Q

when p orbitals overlap, is end to end representing sigma or pi

A

sigma

79
Q

bonding is ____ and anti bonding is _____ (symbols)

A

sigma, sigma star

80
Q

if a bond is symmetric to rotation about the internuclear axis, is it sigma or sigma star

A

sigma

81
Q

when p orbitals overlap, is side to side representing sigma or pi

A

pi

82
Q

which kind of MO is it if the probability of finding an e- between 2 nuclei is lowered

A

antibonding

83
Q

what is the sign of the wave function that changes on 180 degree rotation about the internuclear axis

A

pi

84
Q

look over questions to try at home and answers online from Arnolds notes

A

okayyy

85
Q

why can’t a Px and Py orbitals form

A

they are not symmetric

86
Q

what does a bond order of 3 represent (regarding e- density)

A

there is approximately 3 times the e- density between these 2 nuclei as there would be in a single bond

87
Q

do stable bonds have a positive or negative BO

A

positive

88
Q

is a stable bond, are there more or less e- in bonding orbitals than in anti bonding orbitals

A

more

89
Q

memorize energy order diagram

A

yikes okay

90
Q

what explains the change In sigma2P energy from left to right across a period

A

s-p mixing

91
Q

a high bind order results in a _____ stable molecule

A

more

92
Q

higher bond order correlates to _____ bonds

A

shorter

93
Q

there must be a _____ BO to be stable

A

positive

94
Q

what is a diamagnetic molecule? repelled or attracted to a magnetic field?

A

occurs when all of the e- in the molecule are paired, repelled

95
Q

what is a paramagnetic molecule? repelled or attracted to a magnetic field?

A

occurs when there are unpaired e- in the molecule, attracted

96
Q

when 2 identical atoms form a bond, the resulting MO is _____ over the two atoms

A

spread evenly

97
Q

when atoms of different bonds form MO’s, are they symmetric and spread evenly throughout

A

NOOO

98
Q

what is electronegativity

A

the ability of an atom in am molecule to attract e- to itself

99
Q

what is electronegativity largely driven by

A

Zeff

100
Q

what is the trend for electronegativity

A

increases from left to right across a period and decreases from top to bottom in a group

101
Q

which corner would have the highest electronegativity

A

top right

102
Q

how is electronegativity and ionization energy related

A

parallel, as one increase, so does the other

103
Q

within bonds, _____ e- density is associated with the higher electronegativity element

A

more

104
Q

which a higher electronegativity, the Zeff results in ______ energy

A

lower

105
Q

what is bond polarity

A

a measure of how uneven the distribution of elements in a bond is

106
Q

a bond is polar when the e- are distributed ______ between the elements participating in the bond

A

unevenly

107
Q

a polar bond poses a ______ moment

A

dipole

108
Q

when forming molecular orbitals, the bonding MO has more contribution from the _____ energy orbital, the antibonding MO has more contribution from the ______ energy orbital

A

lower, higher

109
Q

MO’s will look most like the atomic orbital that they are _____ in energy to

A

closest

110
Q

if symmetry is correct, will atomic orbitals always combine to form MO’s

A

no, they need the same energy too

111
Q

what is a nonbonding orbital

A

an atomic orbital for which there is no appropriate match on the other atom to form an MO

112
Q

what is a link between atoms

A

a chemical bond

113
Q

why do bonds form

A

because forming a bond lowers the energy of the electrons and the atoms involved

114
Q

the ionization energy for molecular hydrogen is _____ than for atomic hydrogen

A

larger

115
Q

the e- in molecular hydrogen are _____ in energy than atomic hydrogen

A

lower

116
Q

how are ionization energy and e- energy in a molecule related

A

inversely, as ionization energy increases, the energy of the e- in a molecule decreases

117
Q

lowest energy e- result in the ______ bonds

A

strongest

118
Q

what is the Lennard-Jones potential

A

the balancing of forces the occurs as e- orbitals overlap

119
Q

what procedure is used to combine MO’S mathematically

A

Linear combination of atomic orbitals

120
Q

how can we define the the wave function for the new sigma bonding orbital

A

the sum of the atomic orbital wavefunctions

121
Q

In constructive interference there are two waves that _____ each other

A

reinforce

122
Q

in a MO, where is an e- most likely to be found

A

between the 2 nuclei

123
Q

why do e- in MO’s have lower energy than e- e- in atomic orbitals

A

since the atomic orbitals only experience attraction to one nuclei, it is less stable and has less energy than a molecular orbital where the e- is attracted to two nuclei

124
Q

how is bond stability and energy related

A

inversely, as the bond becomes more stable, the energy becomes lower

125
Q

what is a MO in which there is increased probability of finding e- density between nuclei

A

bonding molecular orbital

126
Q

what is a wave function that is delocalized over the entire molecule

A

a bond

127
Q

whats in-between the nuclei of an antibonding MO

A

a node

128
Q

in an antibonding MO, where is the e- most likely to be found

A

outside of the molecule

129
Q

e- are _____ stable in bonding MO’s than the original atomic orbitals and e- are _____ stable in antibonding MO’s than the original atomic orbitals

A

more, less

130
Q

as MO’s get larger, the e- have _____ wavelengths

A

longer

131
Q

the longer the wavelength, the ______ the energy

A

lower

132
Q

what are the 3 conditions for MO’s to form

A
  1. atomic orbitals must overlap in space
  2. the energies of the atomic orbitals must be similar
  3. the symmetry must be such between the atomic orbitals where overlapping can occur
133
Q

what is the quickest model of bonding often used by chemists

A

lewis dot structures

134
Q

how are e- represented in lewis structures

A

dots

135
Q

what is the rule where atoms lose, gain, or share e- to achieve a noble gas e- config

A

octet rule

136
Q

how are bonds represented in lewis structures

A

a line

137
Q

MO and Lewis structures predict (same or different) bonding

A

same

138
Q

what is the normal valance of an element

A

the number of single bonds it typically forms

139
Q

formal charge of an atom in lewis dot structures is representing the charge it would have if all bonded electrons were ______ between the atoms participating in bonding

A

shared equally

140
Q

whats the formula for formal charge

A

(normal valance e- of an element) - DOTS- LINES

141
Q

if you can’t avoid a formal charge in a lewis structure, which elements should have the charge

A

if its negative, the more electronegative atom

142
Q

if the atom in neutral the formal charge is ____ and if the atom is an ion the charge ____

A

0, must match the charge of the ion

143
Q

whats preferred, a structure with a small or large formal charge attached

A

small

college chem 117 (7 decks)

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