midterm exam 2 Flashcards
(143 cards)
1
Q
what does coulombs law describe the attraction between
A
2 charged particles
2
Q
whats the formula for coulombs law
A
F=kQ1Q2/d^2
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
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
5
Q
what cancels some of the attraction to the nucleus
A
electron-electron repulsion
6
Q
Valance e- are _____/______ from the nuclear charge by the ____ e-
A
screened/shielded, core
7
Q
which formula do we use to account for screening
A
effective nuclear charge
8
Q
what is the formula for effective nuclear charge
A
Zeff = Z-S
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
10
Q
can Zeff ever be larger than the atomic number? Why?
A
No, bc S is always a positive number
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
12
Q
what is the periodic trend for Zeff
A
effective nuclear charge INCREASES from left to right across the period
13
Q
does Zeff have a period trend up or down a group?
A
No it remains the same
14
Q
what is the most important period trend/property
A
Zeff
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
16
Q
how is atomic size defined
A
the distances between the nuclei of atoms
17
Q
what is the metallic radius
A
half the distance between 2 identical adjacent nuclei in a solid metal
18
Q
what is the covalent radius
A
half the distance between 2 adjacent nuclei connected by a covalent chemical bond
19
Q
what is the Van Der Waals radius
A
half the distance between the nuclei of atoms that are touching but not bonding
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
21
Q
what is the periodic trend for bonding atomic radius
A
increases from top to bottom, decreases from left to right
22
Q
which corner of a periodic table has the largest bonding atomic radius
A
bottom left
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
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
25
what does forming an ion require
energy
26
do all elements always form ions
NOOOOO
27
are atomic radii and ionic radii the same size
no, they differ
28
is the radius of Na or Na+ larger
Na
29
is the radius of Cl or Cl- larger
Cl-
30
in general ____ are smaller than the atoms they are derived from and _____ are larger than the atom they are derived from
cations, anions
31
does ionic radius increase up or down a group
down
32
what is an isoelectronic series
a collection of atoms or ions that all have the same number of e-
33
does ionic radius increase or decrease from left to right in a period
decrease
34
which ion is expected to be larger P^3- or S^2-, why?
P^3- because the Zeff of Sulfur is stronger so the e- will be pulled closer in S than in P
35
which ion is expected to be smaller, Cl- or K+, why?
K+, cations are always smaller than anions if isoelectronic
36
what is ionization energy
the minimum energy needed to remove an electron from an atom in a gas phase
37
whats the formula for first ionization energy
X(g) yields X+(g) + e-(g)
38
Since removing an electron requires energy, is IE positive or negative value?
positive
39
what is 1 eV equal to in J
1.602 x 10^-19 J
40
what is the periodic trend of first ionization energy
increases from left to right across a period, decreases from top to bottom within a group
41
which corner would have the highest first ionization energy
top right
42
how are Zeff and ionization energy related
parallel, as Zeff increases, ionization energy increases
43
how are atomic radius and ionization energy related, why?
inversely, as atomic radius increases, the ionization energy decreases because the further from the nucleus an e- is, the less tightly its held
44
what is the second ionization energy
the energy required to remove an e- from an ion with a +1 charge
45
whats the formula for second ionization energy
X+(g) yields X2+(g) + e-(g)
46
which is ALWAYS larger, the first or second ionization energy
the second
47
what is a cause for a drastic increase in ionization energy
when we have to take an e- from the core
48
why is the first ionization energy of boron slightly less than that of beryllium
an exception, the energy of the e- increases slightly upon occupation of the p orbitals
49
why is the first ionization energy of Oxygen slightly less than that of Nitrogen
an exception, the repulsion between 2 electrons within the same 2px orbital makes it slightly easier to remove an e-
50
what is pairing energy
repulsion between e- in the same atomic orbital
51
what is electron affinity
the energy released when an atom in the gas phase accepts an e-
52
whats the formula for e- affinity
X(g) + e-(g) yields X-(g)
53
is ionization energy endothermic or exothermic? electron affinity?
ionization energy is endothermic, electron affinity is exothermic
54
what does a negative EA correspond to
a release of energy during the reaction
55
does exothermic gain or release energy
releases
56
the more _____ the EA, the reaction is more favorable
negative
57
in ionization energy, large values correspond to reactions that require a substantial _____ of energy
input
58
how are the first ionization energy and the electron affinity of an F- ion related
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
why do bonds form
because it lowers the energy
60
does EA have a trend from top to bottom within a group
NOOO
61
what is EA periodic trend
it generally increases from left to right across a period until the noble gasses which are practically 0
62
why is the EA of nitrogen practically 0
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
why does Be have an EA of practically o
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
what are the trends of EA and IE driven by
Zeff and ground state electron configurations
65
look over chart on last page of Geraldine notes
OKAYYY
66
are e- in bonds more or less stable than e- in isolated atoms of the same element
more
67
what is the formula for bond order
BO = (# of bonding electrons - # of anti-bonding electrons)/2
68
do core e- have high or low energy
low
69
why don't core atomic orbitals overlap with orbitals of other atoms
they're too small and too low in energy
70
molecular orbitals are formed between atomic orbitals in the valance shell that have _____ energy and sizes
similar
71
how do the e- fill the orbitals of a MO diagram
increaseing energy, from bottom to top
72
electrons that are ______ in energy than when they are in the atomic orbitals are bonding
lower
73
electrons that are ______ in energy than when they are in the atomic orbitals are antibonding
higher
74
what is the general description of bond order
how many e- are in bonding orbitals relative to antibonding orbitals
75
of molecular orbitals formed is _____ the number of atomic orbitals used to form then
the same as
76
what are the 2 ways p orbitals overlap
side to side, end to end
77
where are you most likely to find an e- in a bonding orbital
in between the two nucleii
78
when p orbitals overlap, is end to end representing sigma or pi
sigma
79
bonding is ____ and anti bonding is _____ (symbols)
sigma, sigma star
80
if a bond is symmetric to rotation about the internuclear axis, is it sigma or sigma star
sigma
81
when p orbitals overlap, is side to side representing sigma or pi
pi
82
which kind of MO is it if the probability of finding an e- between 2 nuclei is lowered
antibonding
83
what is the sign of the wave function that changes on 180 degree rotation about the internuclear axis
pi
84
look over questions to try at home and answers online from Arnolds notes
okayyy
85
why can't a Px and Py orbitals form
they are not symmetric
86
what does a bond order of 3 represent (regarding e- density)
there is approximately 3 times the e- density between these 2 nuclei as there would be in a single bond
87
do stable bonds have a positive or negative BO
positive
88
is a stable bond, are there more or less e- in bonding orbitals than in anti bonding orbitals
more
89
memorize energy order diagram
yikes okay
90
what explains the change In sigma2P energy from left to right across a period
s-p mixing
91
a high bind order results in a _____ stable molecule
more
92
higher bond order correlates to _____ bonds
shorter
93
there must be a _____ BO to be stable
positive
94
what is a diamagnetic molecule? repelled or attracted to a magnetic field?
occurs when all of the e- in the molecule are paired, repelled
95
what is a paramagnetic molecule? repelled or attracted to a magnetic field?
occurs when there are unpaired e- in the molecule, attracted
96
when 2 identical atoms form a bond, the resulting MO is _____ over the two atoms
spread evenly
97
when atoms of different bonds form MO's, are they symmetric and spread evenly throughout
NOOO
98
what is electronegativity
the ability of an atom in am molecule to attract e- to itself
99
what is electronegativity largely driven by
Zeff
100
what is the trend for electronegativity
increases from left to right across a period and decreases from top to bottom in a group
101
which corner would have the highest electronegativity
top right
102
how is electronegativity and ionization energy related
parallel, as one increase, so does the other
103
within bonds, _____ e- density is associated with the higher electronegativity element
more
104
which a higher electronegativity, the Zeff results in ______ energy
lower
105
what is bond polarity
a measure of how uneven the distribution of elements in a bond is
106
a bond is polar when the e- are distributed ______ between the elements participating in the bond
unevenly
107
a polar bond poses a ______ moment
dipole
108
when forming molecular orbitals, the bonding MO has more contribution from the _____ energy orbital, the antibonding MO has more contribution from the ______ energy orbital
lower, higher
109
MO's will look most like the atomic orbital that they are _____ in energy to
closest
110
if symmetry is correct, will atomic orbitals always combine to form MO's
no, they need the same energy too
111
what is a nonbonding orbital
an atomic orbital for which there is no appropriate match on the other atom to form an MO
112
what is a link between atoms
a chemical bond
113
why do bonds form
because forming a bond lowers the energy of the electrons and the atoms involved
114
the ionization energy for molecular hydrogen is _____ than for atomic hydrogen
larger
115
the e- in molecular hydrogen are _____ in energy than atomic hydrogen
lower
116
how are ionization energy and e- energy in a molecule related
inversely, as ionization energy increases, the energy of the e- in a molecule decreases
117
lowest energy e- result in the ______ bonds
strongest
118
what is the Lennard-Jones potential
the balancing of forces the occurs as e- orbitals overlap
119
what procedure is used to combine MO'S mathematically
Linear combination of atomic orbitals
120
how can we define the the wave function for the new sigma bonding orbital
the sum of the atomic orbital wavefunctions
121
In constructive interference there are two waves that _____ each other
reinforce
122
in a MO, where is an e- most likely to be found
between the 2 nuclei
123
why do e- in MO's have lower energy than e- e- in atomic orbitals
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
how is bond stability and energy related
inversely, as the bond becomes more stable, the energy becomes lower
125
what is a MO in which there is increased probability of finding e- density between nuclei
bonding molecular orbital
126
what is a wave function that is delocalized over the entire molecule
a bond
127
whats in-between the nuclei of an antibonding MO
a node
128
in an antibonding MO, where is the e- most likely to be found
outside of the molecule
129
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
more, less
130
as MO's get larger, the e- have _____ wavelengths
longer
131
the longer the wavelength, the ______ the energy
lower
132
what are the 3 conditions for MO's to form
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
what is the quickest model of bonding often used by chemists
lewis dot structures
134
how are e- represented in lewis structures
dots
135
what is the rule where atoms lose, gain, or share e- to achieve a noble gas e- config
octet rule
136
how are bonds represented in lewis structures
a line
137
MO and Lewis structures predict (same or different) bonding
same
138
what is the normal valance of an element
the number of single bonds it typically forms
139
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
shared equally
140
whats the formula for formal charge
(normal valance e- of an element) - DOTS- LINES
141
if you can't avoid a formal charge in a lewis structure, which elements should have the charge
if its negative, the more electronegative atom
142
if the atom in neutral the formal charge is ____ and if the atom is an ion the charge ____
0, must match the charge of the ion
143
whats preferred, a structure with a small or large formal charge attached
small
