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AQA Chemistry AS level and A level > 3 Bonding > Flashcards

3 Bonding Flashcards

1
Q

why do chemical bonds form

A

to achieve a more stable electron arrangement

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2
Q

when are ionic bonds formed

A

when one or more electrons are tranferred from one atom to another

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3
Q

what holds ions together

A

electrotatic attraction

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4
Q

what do groups in the periodic table to form ions

A 
group1 loses 1 electron forming a +1 ion
group2 loses 2 electrons forming +2 ion
group3 loses 3 electrons forming 3+ ion
group4 gains 3 electrons forming 3- ion
group5  gains 2 electrons forming 2- ion
group 7 gains 1 electron forming 1- ion 
group8 dont gain or lose electrons to form ions
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5
Q

what is the formula for a sulphate ion

A

SO4 2-

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6
Q

what is the formula for a hydroxide ion

A

OH-

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7
Q

what is the formular for a nitrate ion

A

NO3-

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8
Q

what is the formula for a carbonate ion

A

CO3 2-

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9
Q

what is the formular for an ammonium ion

A

NH4+

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10
Q

define a giant lattic

A

giant regular arrangement

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11
Q

explain why ionic compounds conduct electricty when they’re moletn or dissolved but not when solid

A

the ions are free to move to carry a charge in a solid all the ions are in fixed position by strong ionic bonds

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12
Q

explain why ionic compounds have high melting points

A

a lot of energy is needed to break the strong ionic bond between the oppositely hcarged ions

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13
Q

explain why ionic compunds dissolve in water

A

water molecules are polar they have a partially positive charge part and partially negative charged part these charged parts pull ions away from the lattice causing it to dissolve

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14
Q

give two examples of ionic compunds

A

NaCl

MgCl2

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15
Q

when do molecules form

A

they form when two or more atoms bond together it doesnt matter if the atoms are the same/different

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16
Q

how does sharing electrons hold atoms together

A

the electrons are held by electrostatic aqttraction between the nuceli and the shared electrons this takes place within the molecule

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17
Q

what is a covalent bond

A

a shared paired of electrons forms when two or more orbitals overlap
is the electrostatic attraction between the positive nucleus of an atom and the bonded pair of electrons

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18
Q

between what type of atoms do covalent bonds form

A

non metals

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19
Q

what is a dative /co ordinate bond

A

where the dative bond contains a shared pair of electrons with both electrons supplied by one atom.

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20
Q

why does dative bonding occur in ammonium ions

A

becvause it forms when the nitrogen atom in an ammonia molecule donates a pair of electrons to a proton H+

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21
Q

how do you represent a dative bond in diagrams

A

and arrow pointing away from the ‘donor’ atom

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22
Q

give another name for giant covalent structures

A

macromolecular structures

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23
Q

what is a giant covalent structure

A

a huge network of covalently bonded atoms

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24
Q

give to examples of giant covalent structures

A

diamond and graphite

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25
Q

why can graphite be used as a lubricant and be used in pencils

A

the week van der waals forces between the layers of graphite eare easily broken so the layers can slide over each other

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26
Q

descirbe the structure of and bonding in graphite and explain why the melting point of graphite is very high

A

the layer of carbon atoms are connected by covalent bonds within each layer there are weak van der waals forces between the layer.A lot of energy is needed to break the strong covalent bonds s

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27
Q

explain why can graphite conduct electricity

A

the delocalised electrons in grahite are not attached to any carbon atoms and are free to move along the sheets carrying a charge

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28
Q

explain why is graphite is insoluble in any solvent

A

the covalent bonds in the sheets are too strong to break

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29
Q

explain why graphite can be used to make strong lightweight sports equipment

A

the layers are far apart vompared to the length of the covalent bonds so graphite has a low density

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30
Q

explain what property makes diamond useful in diamond tipped drills and saws

A

property:hard ,diamond has a strong unlayered rigid 3D structure held be strong covalent bonds

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31
Q

explain why diamond cannot conduct electricity

A

diamond has no free delocalised electrons to carry charge as all the outer electrons are held in localised bonds

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32
Q

explain why is diamond is insoluble in any solvent

A

the covalent bonds in diamonds 3D structure are too strong to break

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33
Q

explain why diamond is a good thermal conductor

A

vibrations travel easily through the stiff lattice

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34
Q

why does diamond sparkles when you cut it

A

its structure makes it refract light a lot

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35
Q

describe the bonding in a crystal of iodine

A

covalent bonds between the atoms

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36
Q

name the crytsal tyep which describes an idoine crystal

A

molecular strcutre

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37
Q

explain why heat energy si required to melt an iodine crytssla

A

the weak van der waals forces must be broken

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38
Q

explain why iodine vaporiesses when heated gently

A

the weak van der waals forces between the iodine molecules are easily broken

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39
Q

why doesnt iodine conduct electricity

A

because there are no charged aprticles to carry charge

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40
Q

explain why iodine has a low boiling boint

A

he weak van der waals forces between the iodine molecules are easily broken

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41
Q

describe the bonding in a metal

A

lattice of poisitve ions embedded in a sea of delocalised electrons

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42
Q

explain why metals have a high metling point

A

a lot of energy is needed to break the strong metallic bond

43
Q

explain why magnesium has a higher melting poitn than sodium

A

magnesium has more protons which attracts the electrons more stronlgyh and so increasing the strength of the mettalic bond requiring more energy to break than the energy reuqired to break the metallic bond of soidum

44
Q

explain why metals can conduct electriciyt

A

the delcoaised electrons can move to carry a charge through the metallic structure

45
Q

explain why metals are thermal conductors

A

the delocalised electrons can pass kinetic negery to each other

46
Q

explain how the charge of an ion affects the strenght of metals

A

the greater the charge on the ion the greater the number of delocaised electrons and the stronger the electrostatic attraction between the positive ions and the electrons and the stronger the metallic bond

47
Q

explain how the size of an ion affects the strength of metals

A

the smaller the ion the closer the electrons are to the positive nucelsu and the stronger the metallic bond

48
Q

explain why metals are ductile

A

the layers in the metal can slide over one another

49
Q

explain hwy metals are malleable

A

after a small distortion each metal ion is in the same environemnt as before keeping the fixed arrangemtn of the metallic structure

50
Q

explain why ionic compunds are brittle

A

s mall displacement will cause contatc between ions with like charges and so they repel casuing the ionic compound to shatter

51
Q

what are the two rules that must happen for dative bonding to occur

A

the atom that accepts the electron pair is an atom that doesn’t have a filled outer main level of electrons

the atom that is donating the electrons has a pair of electrons that is not being used in a bond called a lone pair

52
Q

deine elecotrnegativyt

A

it is a measure of an atms ability to attract a pair of electrons in a covalent bond

53
Q

explain and state the trend in negativity going down a group

A

electronegativty decreases because there is more shieling by electrons which increases the atomic raduis and so the electrostaic force of attrcation decreases

54
Q

explain and state the trend in negativity across a period

A

electronegativity increases because although shieklignis the same nucklear chasrge increases which decreases the atomic raduis and so the electrostaic force of attraction increases

55
Q

what does electron density describe

A

describes the wy the negative charge is distributed in a molecule

56
Q

deine polarity of covalent bonds

A

unequl sharing of electrons between atoms that are bonded together covalently

57
Q

why is the covalent bond non polar between two atoms that are the same

A

the covalent bond is equally shared between the atoms since both atoms have the same electronegativty so the bond is completely non polar

58
Q

why is the covalent bond polar between two different atoms

A

the bond will not be shared equally since the atoms have different electronegativy

59
Q

In hydrogen fluroide why is fluroine end of the molecule relaitively negative and the hydrogen end relatively positive

A

hydrogen has a lower electronegativity than fluroine meaning the electrons in the covalent bond will be attrcated more by fluorine than hydrogen and so the electron cloud is distortewd towards fluroine making the flourine ened of the molecule relatively negative and the hydrogen end of the molecule relaitvely positive

60
Q

what is the relationship between diffrence in electroneativity and polairty of a covalent bond

A

the bgretaer the diffrenece in electronegative the more polar the covalent bond is

61
Q

list the different ytpes of intermolecular forces in order of strength

A

Van der walls forces
dipole-dipole forces
hydrogen bonding

62
Q

where do van der waals forces occur

A

between all atoms and molecules that are non polar

63
Q

why does I2 have a higher boiling point than CL2

A

iodine has more electrons than chlorine so the van der waals force of iodine is stronger and larger than the van der waals forces of chlorine and so more energy is needed to break the van der waals forces between the iodine molecules than the chlorine molecules

64
Q

explain why straight chain alkanes have higher melting point than branched chain alkanes

A

staright chain alkanes can pack closer together than branched alkanes creating more points of contact between the moleculestherefore straight chain alkanes have stronger van der waals forces than branched chain alkanes and so require nore energy to break the van der waal forces between the molecules.

65
Q

where do dipole - dipole forces occur

A

between molecules that have a polar bond

66
Q

how do dipole dipole forces occur in hydrogen chloride

A

chlorine is more electronegative than hydrogen so electrons are pulled towards chlorine rather than hydrogen thefore molecule forms a dipole with paritally poisitve hyfdrogen and partially negative chlorine

67
Q

how will two molecules with dipoles attarct one another

A

whatevere the starting position the molecules with dipoles will flip to give an arrangement where two molecules attract

68
Q

when does hydrogen bonding occur

A

acts when hydrogen of one molecule is attracted to a more electronegative atom on a neigbouring molecule can only occur if the hydrogen is bonded to Fluroine,Oxygen,Nitrogen.

69
Q

why does hydrogen bonding only occur between fluroine oxygen and nitrogen

A

because F,O,N are the only atoms electronegative eneough to form hydrogen bonds

70
Q

how do we represent hydrogen bonds

A

— (dashes)

71
Q

why is water polar

A

oxygen is more electronegative than hydrogen

72
Q

why do the noble gases show a gradual increase in boiling points down the group

A

because the strength of van der waal forces acting between the atoms increases due to more electrons and so increases the strength and size of the van der waals forces down the group and so more and more energy is needed to break the van der waals forces

73
Q

explain why the boiling points of water,hydrogen fluroide and ammonia all higher than the other hydrides of the other elements in their group

A

because hydrogen bonding is present between the molecules in each of the compounds (water,hydrogen fluroide and ammonia) so more energy is needed to break the hydrogen bonding than that of the intermolecular forces between the hydrides.

74
Q

although phosphine molecules,Ph3 contain hydrogen atoms hydrogen bonding doesnt occur sugeest a reason why

A

Phosphoruos and hydrogen have a small electronegativity difference and P is not very electronegative

75
Q

explain the importance of hydrogen bonding in ice

A

as liquid water cools to form ice the molecules make more hydrogen bonds and arrange themselves into a regular lattice structure where the water molecules are further apart on aergae than the molecules in liquid water so ice is less dense than liquid water and so ice forms on top of ponds rather than the bottom insulating the pond and enabling the life of organisms to evolve.

76
Q

explain the importance of hydrogen bonding in ironing

A

the iron provides heat to break the hydrogen bonds in th crumpled material and pressure to make the material flat forcing molecules into new positions.When you remove the iron the hydrogen bonds can reform and hold the molecules in these new positions keeping the fabric flat.

77
Q

What does the electron pair repulsion theory state

A
  • pairs of electrons repel each other so they they are as far apart as possible
  • lone pairs repel slightly more than bonded pairs because they’re more compact
  • the molecule or ion takes up a shape which minimises these repulsions
  • each lone pair reduces the bond angle by 2.5 degrees
78
Q

How to draw a bond in the plain of the paper

A

a line

79
Q

How to draw a bond coming out of the paper

A

a wedge

80
Q

How to draw a bond going into the paper

A

a dotted line

81
Q

what shape is a molecule with 2 electron pairs and no lone pairs and what is the bond angle

A

linear

180

82
Q

what shape is a molecule with 3 electron pairs and no lone pairs and what is the bond angle

A

trigonal planar

120

83
Q

what shape is a molecule with 4 electron pairs and no lone pairs and what is the bond angle

A

tetrehedral

109.5

84
Q

what shape is a molecule with 4 electron pairs and one lone pair and what is the bond angle

A

trigonal pyramid

107

85
Q

what shape is a molecule with 4 electron pairs and two lone pair and what is the bond angle

A

bent

104.5

86
Q

what shape is a molecule with 5electron pairs and no lone pairs and what is the bond angle

A

trigonal bipyramid

120 and 90

87
Q

what shape is a molecule with 5 electron pairs and one lone pairs and what is the bond angle

A

seesaw

102 and 87

88
Q

what shape is a molecule with 5 electron pairs and two lone pairs and what is the bond angle

A

T shaped

88

89
Q

what shape is a molecule with 6 electron pairs and no lone pair and what is the bond angle

A

octahedral

90

90
Q

what shape is a molecule with 3 electron pairs and two lone pairs and what is the bond angle

A

square planar

90

91
Q

describe the steps for predicting the shape of a molecule

A
  1. work out which one is the central atom
  2. use the periodic table to work out the number of electrons in the outer shell of the central atom
  3. add one to this number for every atom that the central atom is bonded to
  4. divide by two to find the number of electron pairs on the central atom
  5. compare the number of electron pairs to the number of bonds to find the number of lone pairs and bond pairs on the central atom
92
Q

describe the steps for predicting the shape of an ion

A
  1. work out which one is the central atom
  2. use the periodic table to work out the number of electrons in the outer shell of the central atom
  3. add one to this number for every atom that the central atom is bonded to
  4. add one for each negative charge on the ion or subtract 1 for each positive charge on the ion
  5. divide by two to find the number of electron pairs on the central atom
  6. compare the number of electron pairs to the number of bonds to find the number of lone pairs and bond pairs on the central atom
93
Q

Why does the shape of a molecule change when a coordinate bond forms

A

Bond pairs repel less than lone pairs so bond angle increases slightly

94
Q

list the following in order of increase repulsion

lone pair-bond pair,lone pair-lone pair,bond pair-bond pair

A

bond pair-bond pair
lone pair -bond pair
lone pair-lone pair

95
Q

what is the effect of lectron pair repulsion on bond angles

A

bond pair-bond pair angles are the smallest
lone pair-bond pair angles are the second biggest
lone pair-lone pair angles are the biggest

96
Q

describve the physical properties of a solid

A

particles are very close together
solids cannot be compressed
particles vibrate about a fixed point and cannot move freely

97
Q

describe the physical properties of a liquid

A

particles are still quite close together but not as much in solids
lquids cannot be compressed
particles move about freely and randomly within the liquid allowing it to flow

98
Q

describe the physical properties of a gas

A

particles are far apart
can be compressed
particles move about freely and rapidly with a lot of energy

99
Q

describe what happens when you heat a solid

A

particles vibrate more about a fixed point distance between the particles slightly increases so solid expands

100
Q

describe what happens when you melt a solid into a liquid (melting-fusion)

A

energy is supplied to weaken the forces that act between the particles holding them toegtehr in the solid state

101
Q

describe what happens when you heat a liquid(

A

you supply more energy to the particles increasing the KE of the particles the particles move a little further apart and so the liquid expands

102
Q

describe what happens when you turn a liquid into a gas (boiling - vapourisation)

A

enegry is needed to break all the intermolecular forces between the particles

103
Q

describe what happens whne you heat a gas

A

the particles gain KE and move faster the particles get much further apart and so the gas expands

AQA Chemistry AS level and A level (12 decks)

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