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Aqa A Level Chemistry > Bonding > Flashcards

Bonding Flashcards

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1
Q

Main two types of bonding

A

Ionic and covalent

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2
Q

When are ions formed?

A

When one or more electrons are transferred from one atom to another

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3
Q

What is ionic bonding

A

When ions are held together by electrostatic attraction

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4
Q

What are the simplest ions?

A

Single atoms which have lost or gained electrons do they’re got a full outer shell

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5
Q

What do elements in the same group have?

A

The same number of outer electrons they want so form ions with same charges

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6
Q

What’s electrostatic attraction?

A

The thing that holds positive and negative ions together. It’s very strong

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7
Q

What are a lot of ions made of?

A

Groups of atoms with no overall charge (compound ions).

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8
Q

Sulfate

A

SO4 3-

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9
Q

Hydroxide

A

OH-

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10
Q

Nitrate

A

NO3 -

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11
Q

Carbonate

A

CO3 2-

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12
Q

Ammonium

A

NH4+

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13
Q

Ionic compounds are made up of?

A

Positively charged parts and negatively charged parts

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14
Q

Overall charge of any compound is?

A

Zero

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15
Q

What must negative charges in a compound do ?

A

Balance all the positive charges

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16
Q

What can you use charges on individual ions present to work out?

A

The formula of an ionic compound

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17
Q

Sodium chloride structure

A

Giant ionic lattice

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18
Q

What are ionic crystals?

A

Giant lattices of ions

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19
Q

What’s a lattice?

A

Just a regular structure

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20
Q

Why’s giant ionic lattice called giant?

A

Because it’s made up of same basic unit repeated over and over again

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21
Q

Sodium chloride describe

A

Na+ and Cl- ions packed together

Sodium chloride lattice is cube shaped- different ionic compounds have different shaped structure

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22
Q

What does the structure of an ionic compound determine?

A

Their physical properties

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23
Q

Ionic compounds properties

A

Conduct electricity when molten or dissolved but not when solid
Have high melting points
Tend to dissolve in water

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24
Q

Why do ionic compounds Conduct electricity when molten or dissolved but not when solid?

A

Ions in a liquid are free to move and carry a charge

In a solid the ions are fixed in position by strong ionic bonds

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25
Q

Why do ionic compounds Have high melting points?

A

Giant ionic lattice held together by strong electrostatic forces. Takes loads of energy to overcome forces so melting points are very high

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26
Q

Ionic compounds Tend to dissolve in water why?

A

Water molecules are polar- part of molecules has a small negative charge and other bit have small positive charges. Charged parts pull ions away from lattice causing it to dissolve

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27
Q

When do molecules form?

A

When two or more atoms bond together. Doesn’t matter if atoms are same or different

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28
Q

Molecules held together by?

A

Strong covalent bonds

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29
Q

What does covalent bond happen between?

A

Non-metals

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30
Q

What’s a single covalent bond?

A

A shared pair of electrons

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31
Q

In covalent bonding what happens?

A

Two atoms share electrons so both full outer shells of electrons. Both positive nuclei are attracted electrostatically to shared electrons

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32
Q

Types of bonds atoms form?

A

Single bonds
Double bonds
Triple covalent bonds

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33
Q

What do multiple bonds contain

A

Multiple pairs of electrons

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34
Q

Describe giant covalent structure

A

Have huge network of covalently bonded atoms

Macromolecular structures

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35
Q

Why can carbon form giant covalent structure?

A

Can form 4 strong, covalent bonds

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36
Q

Graphite structure explains what?

A

It’s properties

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37
Q

What do the weak bonds in graphite do?

A

Weak bonds between layers in graphite are easily broken so sheets can slide over each other.
Graphite feels slippery and is used as a dry lubricant and in pencils

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38
Q

Delocalised electrons graphite?

A

The delocalised electrons in graphite aren’t attached to any particular carbon atoms and are free to move along the sheets carrying a charge. Graphite is an electrical conductor

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39
Q

Layers of graphite?

A

Far apart compared to covalent bonds so graphite is low density and is used to make strong, lightweight sports equipment

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40
Q

Why does graphite have a high melting point?

A

Strong covalent bonds in hexagon sheets.

Graphite very high melting point (sublimes at over 3900K)

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41
Q

Graphite with any solvent?

A

Insoluble

Covalent bonds in sheet are too strong to break

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42
Q

Graphite structure

A

Carbon stone arranged in flat hexagon covalently bonded sheets with three bonds each. Four outer electron of each carbon atom is delocalised

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43
Q

Diamond is the?

A

Hardest known substance

Made if carbon atoms

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44
Q

Diamond structure

A

Each carbon atom is covalently bonded to four other carbon atoms. Atoms arrange in tetrahedral

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45
Q

Because of diamonds strong covalent bonds it?

A 
Has very high melting point 
Extremely hard
Good thermal conductor 
Can't conduct electricity
Won't dissolve in any solvent 
You can cut diamonds to form gemstones
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46
Q

When does diamond sublime?

A

sublimes at over 3900K

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47
Q

What’s diamond used in?

A

used in diamond-tipped drills and saws

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48
Q

Why’s diamond a Good thermal conductor?

A

Vibrations travel easily through stuff lattice

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49
Q

Why can’t diamond conduct electricity?

A

All outer electrons held together in localised bonds

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50
Q

Why does diamond sparkle?

A

It refracts light a lot

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51
Q

What is dative covalent bonding?

A

Where both electrons come from one atom

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52
Q

Describe ammonium ion?

A

Classic example of dative covalent or coordinate bonding

Forms when nitrogen in an ammonia molecule donates a pair of electron to a proton

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53
Q

Molecules and ions come in

A

Loads of different shapes

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54
Q

What does the shape depend on?

A

Electrons in outer shell of central atom

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55
Q

Bonding pairs and lone pairs exist as?

A

Charge clouds

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56
Q

What’s a charge cloud

A

An area where you have a big chance of finding an electron pair. Electrons whizz around inside charge cloud.

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57
Q

When do you get a compound?

A

When different elements or bonds join together

E.g. Elements hydrogen and oxygen make water

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58
Q

What are all what charged and what do the charge clouds do?

A

Negatively charged and so charge clouds will repeal each other as much as they can so pairs of electrons in outer shell of atom sit as far apart from each other as they possibly can

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59
Q

What does the shape of the charge cloud affect?

A

How much it repels other charge cloud. Lone pair clouds repel more then bonding-pair charge clouds

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60
Q

What are the greatest angles between?

A

Lone pairs of electrons and bond angles between bonding pairs are often reduced because they are pushed together by lone-pair repulsion

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61
Q

What are the biggest angle?

A

Lone pairs

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62
Q

What are the second biggest angle?

A

Lone pair/ bonding pair

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63
Q

What are the smallest angles?

A

Bonding-pairs

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64
Q

Explain what is used to display bonds

A

Wedge shows bonds sticking out of page

Broken lines show bonds that go into page

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65
Q

What’s this theory called?

A

Valence-shell electron-pair repulsion theory

66
Q

What do you need to predict a shape of molecule?

A

You need to know how many bonding and lone pairs on central atom of the molecule

67
Q

How to predict shape of molecule

A

First work out central atom (one others are bonded to)
Use periodic table to work out number of electrons in outer shell of central atom
Add 1 to number for every atom that central atom is bonded to
Divide by 2 to find number of electron pairs on central atom
Compare number of electron pairs to number of bonds to find number of lone pairs and number of bonding pairs on central atom

68
Q

What happens if dealing with an ion?

A

You need to take its charge into account

After step 3, add 1 for each negative charge on the ion

69
Q

2 electron pairs?

A

180 degrees
Linear- no lone pairs
Cl-Be-Cl

70
Q

3 electrons pairs

A

120
No lone pairs
trigonal planar

71
Q

Tetrahedral

A

No lone pairs
4 electron pairs
109.5

72
Q

Trigonal pyramidal

A

4 electron pairs
1 lone pair
107

73
Q

Bent

A

2 lone pairs
4 electron pairs
105

74
Q

Trigonal bipyramidal

A

No lone pairs
5 electron pairs
90 in corner
120 side

75
Q

Seesaw

A

1 lone pair
5 electron pairs
87
102

76
Q

T-shaped

A

2 lone pairs
5 electrons
88

77
Q

Octahedral

A

No lone pairs
6 electron pairs
90 in corner right
90 on middle right

78
Q

Square planar

A

2 lone pairs
6 electron pairs
90 degrees

79
Q

Molecules with 5 electrons and 1 lone pair?

A

Pretty rare like octahedral but with bottom Element replaced by a lone pair

80
Q

Example:predicting shape of molecule H2S

A

Central atom is sulfur
Sulfur’s group 6 so has 6 electrons in outer shell
Sulfur atom bonded to 2 hydrogen atoms so had 8 electrons in outer shell in H2S
Sulfur atom has 4 electron pairs and has made 2 bonds so has 2 bonding pairs and 2 lone pair
H2S will have bent shape

81
Q

What’s electro negativity?

A

An atom’s ability to attract electron pairs in a covalent bond

82
Q

What’s the most electronegative element?

A

Fluorine

Oxygen, nitrogen and chlorine also strongly electronegative

83
Q

What makes a bond polar?

A

In a covalent bond two atoms of different electronegatives the bonding electron will be pulled towards the more electronegative atom making the bond polar

84
Q

Why in a covalent bond between 2 atoms of the same element is it non-polar?

A

The atoms have equal electronegativites so ejection are equally attracted to both nuclei

85
Q

What are some elements like carbon and hydrogen?

A

Have pretty similar electronegative so bonds between them are essentially non-polar

86
Q

What happens in a polar bond?

A

The difference in electron in electronegativity between 2 atoms causes a permanent dipole.

87
Q

What’s a dipole?

A

A difference in charge between 2 atoms caused by shift in electron density in the bond

88
Q

Delta means?

A

Slightly

Delta + means slightly positive

89
Q

Why do chlorine and hydrogen form a permanent dipole?

A

Chlorine is much more electronegative than hydrogen

90
Q

Correlation between electronegativity of atoms and polarity?

A

The greater difference in electronegativity between the atoms the more polar the bond

91
Q

What happens if a molecule contains polar bonds?

A

You can end up with an uneven distribution of charge across the whole molecule. When this happens, the molecule is polar

92
Q

Do all molecules that contain polar bonds be polar?

A

No. If polar bonds are arranged symmetrically in the molecule then the charges cancel out and there is no dipole

93
Q

In a substance made up of molecules with permanent dipoles?

A

There will be weak electrostatic forces of attraction between delta + and delta - on neighbouring molecules

94
Q

If you put a charged rod next to a jet of polar liquid e.g. Water what happens

A

The liquid will move towards the rod because polar liquid contains molecule with permanent dipole.
Doesn’t matter if rod is positively or negatively charged. Polar molecules in liquid can turn around so opposite charged end attracted towards the rod

95
Q

What are intermolecular forces?

A

Forces between molecules

Much weaker than covalent, ionic or metallic bonds

96
Q

Weakest intermolecular force

A

Induced dipole-dipole

van der Waals

97
Q

Middle intermolecular force strength

A

Permanent dipole-dipole forces

Ones caused by polar molecules

98
Q

Strongest electrostatic intermolecular forces?

A

Hydrogen bonding

99
Q

Why are intermolecular force important?

A

Affect physical properties of a compound

100
Q

Van der Waals forces found

A

Between all atoms and molecules

Cause all atoms and molecules to be attracted to each other

101
Q

What are electrons in a charge cloud always doing?

A

Moving very quickly
At any moment, the electrons in an atom are likely to be more to one side than other. At this moment the atom would have a temporary dipole

102
Q

What do dipole cause

A

Another temporary dipole in the opposite direction on a neighbouring atom. The two dipoles are attracted to each other

103
Q

What can the second dipole cause?

A

A third dipole in a third atom

Like domino effect

104
Q

What happens because electrons are constantly moving?

A

Dipoles being created and destroyed all the time. Even though dipoles keep changing overall effect is for atoms to be attracted to each other

105
Q

Why is iodine a solid at room temperature?

A

Van der Waals forces between iodine molecules that are responsible for holding them together in a lattice

106
Q

Forces and bonds of solid iodine

A

Iodine atoms are held together in pairs by strong covalent bonds to form I2 molecules
Molecules held together by molecular lattice arrangement by weak van der Waals

107
Q

Strengths of Van der Waals?

A

Aren’t all same strength

Larger molecules have larger electron clouds meaning stronger van der Waals forces

108
Q

What does shape of molecules have to do with van der Waals?

A

Shape of molecule affects strength of Van der Waal forces
Long, straight molecules lie closer together than branched ones
The closer together 2 molecules get the stronger the forces between them are

109
Q

What happens as you boil a liquid?

A

You need to overcome intermolecular forces so particles can escape from liquid surface. Stands to reason you need more energy to overcome stronger intermolecular forces so liquids with stronger van der Waals forces will have high boiling points

110
Q

As alkane chains get longer

A

The number of electrons in the molecules increases

Meaning stronger van der Waals so boiling point increases

111
Q

What else does Van der Waals affect?

A

Other physical properties e.g. Melting point and viscosity

112
Q

When does hydrogen bonding happen?

A

Only when hydrogen is covalently bonded to fluorine, nitrogen or oxygen

113
Q

Why does hydrogen bonding happen with fluorine, nitrogen and oxygen?

A

They are very electronegative so draw bonding electrons away from hydrogen atoms. Bond is polarised and hydrogen has such a high charge density (so small) that hydrogen the hydrogen atoms form weak bonds with lone pairs of electrons on fluorine, nitrogen or oxygen atoms of other molecules

114
Q

What two groups do hydrogen bonding usually contain?

A

-OH or -NH groups

115
Q

Water and ammonia both have?

A

Hydrogen bonding

116
Q

Substances with hydrogen bonding melting and boiling points?

A

Higher then other similar molecules because extra energy is needed to break the hydrogen bonds
Water and hydrogen fluoride has a much higher boiling point than other hydrogen halides

117
Q

What happens as water cools to form ice?

A

Molecules make more hydrogen bonds and arrange themselves in a regular lattice structure
In regular structure H2O molecules are further apart on average than molecules in liquid water so ice is less dense than liquid water

118
Q

Metal elements exist as?

A

Giant metallic lattice structure

119
Q

Giant metallic lattice describe

A

Outermost shell of metal atom electrons are delocalised- electrons move about metal leaving positive ion e.g. Na+…
Positive metal ions attracted to delocalised negative electrons form lattice of closely packed positive ions in sea of delocalised electrons (metallic bonding)

120
Q

Why do metals have high melting point?

A

Strong electrostatic attraction between positive ions and delocalised sea of electrons

121
Q

What also affects melting point of metals?

A

Number of delocalised electrons per atom. The more there are the stronger the bonding will be and the higher the melting point. E.g.?Mg2+ has 2 delocalised electrons per atom got a higher melting point than Na+ which has 1

122
Q

What are metals good thermal conductors

A

Delocalised electrons can pass kinetic energy to each other

123
Q

What makes metal a good electrical conductor?

A

Delocalised electrons can move and carry a current

124
Q

Why are metals insoluble except liquid metals?

A

Because of strength of metallic bonds

125
Q

Typical solid

A

Particles are very close together

Give a high density and make it incompressible. Particles vibrate about a fixed point and can’t move about freely

126
Q

Typical liquid

A

Similar density to a solid

Virtually incompressible. The particles move about freely and randomly within the liquid allowing it to flow

127
Q

Gases

A

Particles have loads more energy and much further apart
Density generally pretty low and very incompressible. The particles move about freely with not a lot of attraction between them so they’ll quickly diffuse to fill container

128
Q

What do you need to do to change from a solid to a liquid or a liquid to gas?

A

You need to break forces that are holding the particles together. To do this you need to give the particles more every by hearing them

129
Q

To melt or boil a simple covalent compound?

A

You only have to overcome the intermolecular forces that hold the molecules together
Don’t need to break stronger Covalent bonds that hold atom together in molecules. Causes simple covalent compounds to have a low melting and boiling point.

130
Q

Water boiled

A

Stream

131
Q

Describe chlorine

A 
Cl2
Simple covalent substance
Melting point of -101 oC 
Boiling point of -34oC
Gas at room temperature and pressure
132
Q

Describe pentane

A 
C5H12
Simple covalent compound
Melting point of -130 oC
Boiling point of 36oC
Liquid at room temperature and pressure
133
Q

Diamond contrast describe

A

Giant covalent substance
Have to break covalent bonds between atoms to turn to liquid or gas
Never really melts
Sublimes at over 3600oC

134
Q

Melting point and boiling point determined by?

A

Strength of attraction between particles

135
Q

When will a substance conduct electricity

A

If it has charged particles that are free to move

136
Q

How soluble a substance is water depends on?

A

Type of particles it contains
Water polar solvent so substances that are polar or charged will dissolve in it well whereas non-polar or uncharged substances won’t

137
Q

Ionic bonding

Examples

A

NaCl

MgCl2

138
Q

Ionic bonding

Melting and boiling?

A

High

139
Q

Typical state at room temperature and pressure

Ionic bonding

A

Solid

140
Q

Ionic bonding

Liquid and solid conductivity

A

Solid doesn’t because ions held in place

Liquid does ions are free to move

141
Q

Ionic bonding

Water solubility

A

Yes

142
Q

Simple covalent
Molecular
Examples

A

CO2
I2
H2O

143
Q

Melting point and boiling point of simple covalent molecular molecules?

A

Low because it involves breaking intermolecular forces but not covalent bonds

144
Q

Typical state at room temperature and pressure

simple covalent molecular molecules

A

May be solid like I2 but usually liquid or gas

145
Q

simple covalent molecular molecules

Does solid conduct electricity?

A

No

146
Q

simple covalent molecular molecules

Does liquid conduct electricity?

A

No

147
Q

simple covalent molecular molecules

Is it soluble in water?

A

Depends how polarised the molecule is

148
Q

Giant covalent macromolecular examples

A

Diamond
Graphite
SiO2

149
Q

Giant covalent macromolecular

Melting and boiling points?

A

High

150
Q

Giant covalent macromolecular

Typical state at room temperature and pressure?

A

Solid

151
Q

Giant covalent macromolecular

Does it conduct electricity?

A

No except graphite

152
Q

Giant covalent macromolecular

Does the liquid conduct electricity?

A

N/A

Sublimes rather than melting

153
Q

Giant covalent macromolecular

Is it soluble in water?

A

No

154
Q

Metallic examples

A

Fe
Mg
Al

155
Q

Metallic melting and boiling point?

A

High

156
Q

Metallic typical state at room temperature and pressure?

A

Solid

157
Q

Metallic does it conduct electricity when solid?

A

Yes delocalised electrons

158
Q

Metallic does it conduct electricity when liquid?

A

Yes delocalised electrons

159
Q

Is metallic soluble in water?

A

No

160
Q

What can you predict using a materials properties?

A

It’s structure

161
Q

Substance X has a melting point of 1045K. When solid, it is an insulator, but once melted it conducts electricity. Identify the type of structure present in substance X
Workings

A

1) substance X doesn’t conduct electricity when solid but does conduct electricity once melted so looks ionic. Fits with high melting point
2) isn’t simple covalent because of high melting point. Isn’t metallic because doesn’t conduct electricity when solid isn’t giant covalent as conducts electricity when melted

162
Q

Substance X has a melting point of 1045K. When solid, it is an insulator, but once melted it conducts electricity. Identify the type of structure present in substance X
Answer

A

Substance X must be ionic

Aqa A Level Chemistry (12 decks)

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