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IB Chemistry HL > 4/14 chemical bonding and structure > Flashcards

4/14 chemical bonding and structure Flashcards

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1
Q

which elements have ionic bonding

A

metals : non metals

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2
Q

which elements have covalent bonding

A

non-metals

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3
Q

what elements have metallic bonding

A

metals

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4
Q

important point of ionic bonding

A

electron transfer

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5
Q

important point of covalent bonding

A

shared pair of electrons

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6
Q

important point of metallic bonding

A

sea of deloaclised electrons

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7
Q

an ionic bond is…

A

electrostatic attraction

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8
Q

a covalent bond is…

A

shared pair of electrons

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9
Q

a metallic bond is…

A

sea of delocalised electrons

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10
Q

melting point of ionic bond

A

high (must break all ionic bonds)

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11
Q

melting point of covalent giant

A

high (must break all covalent bonds)

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12
Q

melting point of covalent molecular

A

low (often gas at room temp) must only break intermolecular forces)

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13
Q

melting point of metallic

A

high

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14
Q

do ionic compounds conduct electricity

A

molten can, solid cannot

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15
Q

do covalent compounds conduct electrivity

A

no

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16
Q

do metallic compounds conduct electricity

A

yes

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17
Q

what is moving when electricity is conducted in ionic

A

the ions as they have been made free to move

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18
Q

what is moving when electricity is conducted in metallic

A

the delocalised electrons

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19
Q

what is electronegativity

A

the measure of the attraction of the atom for a shared pair of electrons

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20
Q

what does the difference in electronegativity determine

A

the type of bonding that takes place between atoms

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21
Q

a large difference in electronegativity results in

A

the formation of an ionic bond

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22
Q

a small difference in electronegativity results in

A

the formation of a covalent bond

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23
Q

≥ 1.8 units type of bonding

A

ionic

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24
Q

0.5-1.7 units type of bonding

A

polar covalent

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25
Q

0.1 - 0.4 units type of bonding

A

non polar (weakly polar) covalent

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26
Q

0 units type of bonding

A

pure covalent

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27
Q

exceptions to the units type of bonding

A

C-H and H-F

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28
Q

where are non polar covalent bonds used

A

between atoms that are that same element like molecular oxygen

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29
Q

what creates a bond dipole

A

the unequal sharing of electrons in a covalent bond

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30
Q

how do you show a bond dipole

A

δ+ and δ- signs

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31
Q

what are single walled nanotubules made from

A

graphite sheets

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32
Q

what can nanotubules act as

A

conductors or semi conductors

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33
Q

nanotubule properties

A

high electrical conductivity
high thermal conductivity
very very strong
high strain to failure ratio

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34
Q

what has the synthesis of carbon nanotubules enable

A

a way of controlling chemcial reactions on a very small scale. one end can have a fullerene cap so its closed off

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35
Q

what does the octet rule say

A

the most stable arrangement for an atom is to have eight electrons in its outermost energy level with the electron configuration of a noble gas.

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36
Q

what are lewis structures

A

dot and cross diagrams

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37
Q

when are there exceptions to the octet rule

A

atoms that are stable with less than eight electrons and those that can have an expanded octet (more than eight electrons) in their valence shells.

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38
Q

what are the exceptions to the octet rule

A

hydrogen is stable with 2 in outer shell
boron, beryllium and aluminium (in compounds) are stable with fewer than eight electrons in their outer shell.
atoms in period three and higher can form expanded octets with up to twelve electrons in their valence shell

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39
Q

what are atoms that have less than eight electrons in their outer shell

A

incomplete octets or be electron deficient

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40
Q

expanded octets

A

molecules with central atoms from elements in period 3 can accommodate up to 12 electrons in their valence shells.

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41
Q

what does the Valence Shell Electron Pair Repulsion Theory allow us to do

A

predict the shapes of molecules

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42
Q

outline VSEPR

A

electron pairs in molecules repel eachother and orientate themselves as far away from eachother as possible.

a molecule will adopt the shape that minimises the repulsion between the electron pairs.

electron pairs can either be bonding electrons or non-bonding electrons.

both bonding electrons and non-bonding electrons are collectively known as electron domains.

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43
Q

what counts as one electron domain

A

single, double and triple covalent bonds.

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44
Q

what is a bonding domain

A

an electron domain that contains bonding pairs of electorns

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45
Q

what is a non bonding domain

A

an electron domain that contains non-bonding electrons

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46
Q

what are non bonding pairs of electrons also known as

A

lone pairs

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47
Q

order of repulsion between non-bonding and bonding domains

A

Non-bonding domain–non-bonding domain > non-bonding domain–bonding domain > bonding domain–bonding domain

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48
Q

where is the greatest repulsion between

A

between non-bonding domains (lone pairs of electrons), with the second being between non-bonding domains and bonding domains and the least repulsion being between bonding domains.

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49
Q

what type of molecular geometry do molecules with two electron domains around the central atom have

A

linear

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50
Q

what is the bond angle of linear molecular geometry

A

180 degrees, allowing the electrons to be as far apart as possible, which minimises the repulsion between the molecule.

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51
Q

what type of molecular geometry do molecules with three electron domains have

A

trigonal planar. this can either be trigonal planer or bent, depending on the presence of lone pairs of electrons.

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52
Q

how is bent molecular geometry caused

A

by the stronger repulsion that exists between the non - bonding electrons on the central atom compared to the weaker repulstion that exists between the bonding electrons

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53
Q

what is the bond angle for trigonal planar

A

120 degrees

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54
Q

a molecule or ion that has a lone pair of electrons on the central atom of a trigonal planar molecule will have a bond angle of…

A

just under 120 degrees, e.g 117.5

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55
Q

what type of molecular geometry do molecules with four electron domains have

A

tetrahedral electron domain geometry. the molecular geometry can either be tetrahedral, trigonal pyramidal or bent, depending on the number of lone pairs of electrons present.

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56
Q

what type of molecular geometry do molecules with four electron domains have with no lone pairs of electrons

A

tetrahedral

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57
Q

what type of molecular geometry do molecules with four electron domains have with one pair of lone electrons

A

trigonal pyramid

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58
Q

what type of molecular geometry do molecules with four electron domains have with two lone pairs of electrons

A

bent

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59
Q

what bond angle do molecules with four electron domains have with no lone pairs of electrons

A

109.5

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60
Q

what bond angle do molecules with four electron domains have with one pair of lone electrons have

A

107

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61
Q

what bond angle do molecules with four electron domains have with two lone pairs of electrons

A

104.5

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62
Q

why do bond angles become progressively smaller

A

because of the stronger repulsion between the lone pairs and the bonding pairs on the central atom

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63
Q

how can there be molecules with five and six electron domains around the central atom

A

certain atoms in period 3 onwards can expand their octets due to more availability of d orbitals

64
Q

what is the type fo molecular geometry for atoms with five electron domains

A

trigonal bipyramid

65
Q

what is the type of molecular geometry for atoms with six electron domains

A

octahedral

66
Q

what bond angle do molecules with six bonding domains have

A

90 and 180

67
Q

what type of molecualr geometry do molecules with five bonding domains and one non-bonding domain around the central atom have

A

square pyramidal

68
Q

what bond angle do molecules with five bonding domains and one non-bonding domain around the central atom have

A

less than 90, due to extra repulsion between bonding and non bonding domains around the central atom.

69
Q

what type of molecualr geometry do molecules with four bonding domains and two non-bonding domain around the central atom have

A

sqaure planar

70
Q

what type of molecular geometry do molecules with five electron domains have

A

trigonal bipyramid

71
Q

what bond angle do do molecules with five electron domains have

A

90 and 120

72
Q

what type of molecular geometry do molecules with five electron domains have and one lone pair of electrons

A

see saw

73
Q

what type of molecular geometry do molecules with five electron domains have and three lone pairs of electrons

A

T-shaped

74
Q

what type of molecular geometry do molecules with five electron domains have and three lone pairs of electrons

A

linear

75
Q

what bond angle do molecules with five electron domains have and one lone pair of electrons

A

90 and 120

76
Q

what bond angle do molecules with five electron domains have and two lone pair of electrons

A

less than 90

77
Q

what bond angle do molecules with five electron domains have and three lone pair of electrons

A

180

78
Q

electron domain geometry of an atom with 6 electron domains and no non-bonding domains

A

octahedral

79
Q

electron domain geometry of an atom with 6 electron domains and one non-bonding domain

A

octahedral

80
Q

electron domain geometry of an atom with 6 electron domains and two non-bonding domains

A

octahedral

81
Q

molecular geometry of of an atom with 6 electron domains and no non-bonding domains

A

octahedral

82
Q

molecular geometry of an atom with 6 electron domains and one non-bonding domain

A

square pyramidal

83
Q

molecular geoemtry of an atom with 6 electron domains and two non-bonding domains

A

square planar

84
Q

what is the bond angle of a molecule with 6 electron domains with no non bonding domains

A

90

85
Q

intermolecular

A

between seperate molecules

86
Q

intramolecular

A

within molecules, eg covalent bonds, attraction between atoms

87
Q

when do london forces increase

A

when there are more electrons in the molecule

88
Q

what are london forces referred to

A

van de waals
instantaneous dipole
dispersion forces

89
Q

how are instantaneous dipoles created

A

when molecules approach one another and their electron cloud repel each other and create an instantaneous dipole

90
Q

are dipole dipole forces more or less strong than the london forces

A

more

91
Q

a bigger dipole makes for…

A

a stronger interaction

92
Q

when do hydrogen bonds occur

A

when a H atom is directly bonded to a NOF

93
Q

what is special about NOF

A

they are the most electroegative

94
Q

why does hydogen bonding only occur when directly bonded to a NOF

A

NOF are very electronegative and pull the electron away from the H giving it a poitive charge/induced dipole.
the H can interact with a lone pair on the NOF atom. this is the strongest type of intermolecular force.

95
Q

what is the order of strength for forces

A

london forces

96
Q

what type of force do all molecules have

A

london forces

97
Q

properties of metals

A

good conductors of heat and electricity,
ductile (can be made into wires),
malleable (can be bent into shape) and
shiny when polished.

98
Q

describe the electrons in metallic bonding

A

delocalised. can flow and carry charge throughut the substance.

99
Q

describe metallic bonding

A

The metal atoms are ionised, forming positive ions that are arranged in a lattice structure. The bonding in metals, the metallic bond, is defined as the electrostatic attraction between the lattice of positive metal ions and the ‘sea’ of delocalised electrons. Metallic bonding, like ionic bonding, is described as being non-directional, as the force of attraction occurs in all directions between the positive ions and delocalised electrons within the lattice structure.

100
Q

what is a metallic bond

A

the electrostatic attraction between the lattice of positive metal ions and the sea of delocalised electrons

101
Q

how are metals malleabel

A

the layers of positive ions can slide over eachother without disrupting the metallic bond.

102
Q

how are metals ductile

A

the layers of positive ions can slide over eachother without disrupting the metallic bond.

103
Q

what does being ductile mean

A

drawn into wires essentially

104
Q

what causes high thermal and electrical condcutivity of metals

A

the delocalised electrons

105
Q

how do metals conduct electicity

A

When a potential difference (voltage) is applied across a metal, a direction is imposed on the movement of the delocalised electrons. They are repelled from the negative electrode and move towards the positive electrode. This orderly flow of delocalised electrons in a given direction constitutes the flow of an electric current.

106
Q

how do metals conduct heat

A

The delocalised electrons can also conduct heat: the electrons move through the metal, carrying kinetic energy (in the form of vibrations) from the hotter part of the metal to the colder part of the metal. These delocalised electrons are also responsible for the shininess of metals, because they reflect wavelengths of visible light.

107
Q

what effects metal’s melting points

A

the ionic charge: greater number of delocalised electrons increases force of attraction between nuclei and sea
the ionic radii: stronger force of attraction between nuclei and delocalsied electrons

108
Q

why are alloys stronger than pure metals

A

the differently sized atoms in the alloy means that the layers cannot slide over each other as easily

109
Q

brass composition

A

copper
zinc

110
Q

bronze composition

A

copper
tin

111
Q

mild steel composition

A

iron
carbon

112
Q

stainless steel composition

A

iron
chromium
nickel

113
Q

solder composition

A

tin
lead

114
Q

alloys are usually

A

stronger
more chemically table
more resistant to corrosion

115
Q

what type of solvent is water

A

water molecules are polar (and there are hydrogen bonds between molecules)

116
Q

what type of solvent are alkanes

A

non polar
(and there are van der waals / london dispersion forces between the molecules)

117
Q

solubility of ionic compounds in water

A

many ionic compounds dissolve in water
this is because attractions form between the polar water molecules and the ions.

118
Q

solubility of ionic compounds in alkanes

A

insoluble

119
Q

solubility of compounds with hydrogen bonding in water

A

usually dissolve in water.
water has hydrogen bonds and substances with hydrogen bonds can form attractions through hydrogen bonds to the water molecules

120
Q

solubility of compounds with hydrogen bonding in alkanes

A

usually insoluble or only slightly soluble

121
Q

solubility of non polar substances in water

A

usually insoluble or only slightly soluble

122
Q

solubility of non polar substances in alkanes

A

usually dissolve well, intermolceular forces form between the solvent and solute molecules.

123
Q

what is the general phrase of solubility

A

like dissolves like

124
Q

electron geometry is

A

arrangement of electron pairs around the central atom excluding lone pairs

125
Q

molecular geometry is

A

arrangement of atoms including lone pairs

126
Q

what elements can accomodate more than eight electrons in their valence shells

A

period 3

127
Q

why can period 3 elements have expanded octets

A

due to the availability of d orbitals which can be used for bonidng

128
Q

how is signam bond formed

A

by the direct head-on (axial) overlap of atomic orbitals. Figure 1 shows the bonding between two hydrogen atoms in a molecule of hydrogen. The two 1s atomic orbitals overlap head-on, forming a sigma bond.

129
Q

where is electron dnesity in a sigma bond

A

in the region directly between the nuclei of the bonding atoms; this can also be described as cylindrical symmetry along the bond axis (Figure 2). This allows free rotation around a σ bond.

130
Q

sigma bonds can be formed by

A

head on overlap of two s orbitals
s and p orbitals
or two p orbitals

131
Q

how are pi bonds formed

A

sidequas overlap of atomic orbitals (two unhybridised p orbitals)

132
Q

double bond is formed from

A

one sigma bond and one pi bond

133
Q

tripe bond is formed from

A

one sigma bond and two pi bonds

134
Q

which is the stronger bond pi or sigma

A

sigma (from the greater overlap of atomic orbitals

135
Q

FC =

A

(number of valence electrons) - 1/2(number of bonding electrons) - (number of non-bonding electrons
v-1/2B-L

136
Q

what are delocalised electrons

A

electron shared between more than two nuclei. originate from the overlap of pi bonds in a molecule or ion.

137
Q

carbonate ion

A

The carbonate ion is a polyatomic ion consisting of a central carbon atom bonded to three oxygen atoms in a trigonal planar arrangement. The bonds between the carbon and oxygen atoms are sigma bonds formed by the head-on overlap of atomic orbitals. A pi bond is formed by the sideways overlap of the p orbitals on the carbon atom and one of the oxygen atoms. The remaining electrons in the p orbitals of the other two oxygen atoms can overlap with the π orbital (of the pi bond), creating a delocalised pi system (Figure 1). These delocalised pi electrons are spread over all three bonding positions, lowering the energy of the molecule (known as the resonance energy
The intermediate nature of the bonding in the carbonate ion, represented by the dotted lines in the resonance hybrid structure (Figure 2), is explained by the formation of the delocalised π system located above and below the plane of the ion.

138
Q

ethanoate ion

A

In the ethanoate ion, the delocalised π system extends only in the COO− region. Note that this delocalisation of pi electrons does not take place in the ethanoic acid molecule, because one oxygen atom in the carboxyl group is bonded to a hydrogen atom. The resonance hybrid structure of the ethanoate ion is shown in Figure 4. The delocalised electrons are represented by the dashed lines that extend over the COO− region.

139
Q

benzene

A

The benzene molecule has six carbon atoms, each with a single hydrogen atom attached, in a trigonal planar arrangement. The carbon atoms are sp2 hybridised, each with an unhybridised p orbital (note that hybridisation is covered in more detail in section 14.2.1). As with all molecules with delocalised π electrons, benzene can be represented by different resonance structures. The delocalised π system in benzene contains six electrons, one from each of the unhybridised p orbitals in the carbon atoms. These p orbitals overlap to form a delocalised π system located above and below the plane of the benzene ring (Figure 5).

140
Q

ethanoate ion resonance

A
141
Q

carboante resonsance hybrid

A
142
Q

3 possible resonance structures fo rcarboante

A
143
Q

how are all reonance structure of carbonate equal energy

A

Each of the three resonance structures contributes to the hybrid structure depending on its energy, with the resonance structure with the lowest energy contributing the most to the hybrid structure. Because of their symmetry, the three resonance structures of the carbonate ion are all of equal energy and they make equal contributions to the resonance hybrid, referred to as equivalent resonance structures.

144
Q

which structures are the msot stable

A

resonance hybrid always

145
Q

The difference in energy between the resonance hybrid structure and that of the most stable resonance structure is known as

A

the resonance energy

146
Q

nitrite and nitrate ion resonance hybrid structure.

A

nitrite then nitrate

147
Q

elements in perido 3 and beyond can

A

can accommodate more than eight electrons in their valence shells. This is due to the availability of d orbitals which can be used for bonding.

148
Q

how many electrons can sulfur hold in its outer shell

A

12

149
Q

resonance structures of sulfate

A
150
Q

resonance structure of ozone

A
151
Q

Without human influences, the concentration of ozone in the atmosphere remains constant, because

A

the rate of production of ozone is equal to its rate of destruction.

152
Q

what speeds up ozone depletion

A

human-made pollutants such as CFCs and nitrogen oxides disrupt this process, causing the phenomenon of ‘ozone depletion’.

153
Q

give the equation for trichlorofluromethan edecomposing

A

CFCl3 → •CFCl2 + Cl• (occurs in the presence of UV radiation)

154
Q

give the equation for the cataluytic cyle breaking down ozone to form diatomic oxygen molecules

A

Cl• + O3 → ClO• + O2 and ClO• + O• → Cl• + O2

155
Q

equation for overall ozone catayltic cycle (mergin og equations)

A

O3 (g) + O• (g) → 2O2 (g)

156
Q

where are nitrogen ozides produced

A

int he stratoshere in jet engines

157
Q

equations for nitrogen oxids in ozone

A

N2 (g) + O2 (g) → 2NO• (g)

Nitrogen monoxide reacts with ozone as follows:

Step 1: NO• (g) + O3 (g) → NO2• (g) + O2 (g)

Step 2: NO2• (g) + O• (g) → NO• (g) + O2 (g)

combine

O3 (g) + O• (g) → 2O2 (g)

IB Chemistry HL (12 decks)

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