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Higher Chemistry Unit 1: Chemical changes and structure > Structure and Bonding > Flashcards

Structure and Bonding Flashcards

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1
Q

What is metallic bonding?

A

The electrostatic force of attraction between positively charged ions and declocalised electrons.

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2
Q

What is meant by delocalised electrons?

A

The electrons in the outer shell of metal atom move freely through the atoms in the lattice.

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3
Q

Why do metals conduct electricity?

A

Because of the free moving electrons, the delocalised electrons

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4
Q

What does the structure of metals consist of?

A

a giant lattice of positively charged ions and declocalised electrons

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5
Q

What is ionic bonding?

A

the electrostatic attraction between the positive ions of one element (usually metals) and the negative ions of another element (usually non-metals).

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6
Q

What does the structure of ionic compounds consist of?

A

giant lattice of oppositely charged ions

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7
Q

How do atoms form ionic bonds and by doing so what do they achieve?

A

by giving away or receiving electrons. By doing so they achieve a stable electron arrangement .

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8
Q

What is covalent bonding?

A

The electrostatic force of attraction between two positive nuclei and a shared pair of electrons

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9
Q

What is a covalent bond the result of?

A

two positive nuclei being held together by their attraction for a shared pair of electrons.

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10
Q

What does covalent bonding generally occur between?

A

non-metals

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11
Q

What can covalent bonds either be?

A

polar or non-polar

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12
Q

What are polar covalent bonds formed between?

A

atoms with different electronegativies

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13
Q

What will an atom with the higher electronegativity have?

A

a permanent slightly negative charge

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14
Q

What will an atom with the lower electronegativity have?

A

a permanent slightly positive charge

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15
Q

What are delta+ and delta- known as?

A

permanent dipoles

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16
Q

What non-polar covalent bonds formed between?

A

atoms with the same electronegativities

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17
Q

What type of bonds exist as part of the bonding continuum?

A

Pure covalent bonds
Polar covalent bonds
Ionic bonds

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18
Q

How is the type of bonding in a compound determined?

A

By the difference in electronegativity between the elements involved

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19
Q

What is the type of bonds when the difference in electronegativity is zero?

A

Pure covalent bond.

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20
Q

What is the type of bonds when the difference in electronegativity is low?

A

Polar covalent bond

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21
Q

What is the type of bonds when the difference in electronegativity is high?

A

Ionic bond

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22
Q

What do polar covalent bonds tend to have? e.g. H-F

A

polar covalent structures

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23
Q

What do some polar covalent bonds not have?

A

polar covalent structure

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24
Q

Give examples of molecules that have polar covalent bonds but don’t have polar covalent structures?

A

carbon dioxide
tetrachloromethane
methane

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25
Q

Why do some polar bonds not have polar covalent structures?

A

Because of the position of the bonds. The bonds are symmetrically opposed and will cancel out

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26
Q

What are intermolecular forces?

A

the attractive forces which hold molecules together i.e. between molecules. The are often also called Van der Waals’ forces

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27
Q

What are the 3 main types of Van der Waals’ forces?

A
  1. London Dispersion Forces
  2. Permanent dipole-permanent dipole interactions
  3. Hydrogen bonds
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28
Q

What are London dispersion forces out of all the intermolecular forces and what do they occur between?

A

they are the weakest

occur between all atoms and molecules

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29
Q

What are London dispersion forces caused by?

A

the uneven distribution of electrons which are constantly moving in an atom. This forms a temporary dipole on an atom.

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30
Q

What does the uneven distribution of electrons in London dispersion forces form?

A

This forms a temporary dipole on an atom.

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31
Q

What can the atom which has a temporary dipole can do?

A

induce a dipole in a nearby atom

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32
Q

What is a London dispersion force?

A

an attraction between the temporary dipole and the induced dipole

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33
Q

Give two examples of london dispersion forces?

A

Unreactive noble gases are held together by london dispersion forces and the covalent network layers in graphite are held together by london dispersion forces

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34
Q

Describe the trend between the London dispersion forces and the number of electrons in an atom or molecule?

A

As the number of electrons increases in an atom or molecule, the london dispersion forces also increases

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35
Q

When a substance melts or boils, what is broken?

A

intermolecular forces

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36
Q

Describe what happens to the melting/boiling points as we descend down the group of noble gases?

A

they steadily increase

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37
Q

Describe the trend between going down a group and the london dispersion forces?

A

The number of electrons increases going down the group of noble gases. This means the London dispersion forces are becoming stronger. Due to this. more energy is required to overcome the increasing force of attraction. As a result, the melting/boiling points increases.

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38
Q

What are permanent dipole-permanent dipole interactions?

A

They are intermolecular forces of attraction between polar covalent molecules.

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39
Q

When do permanent dipole-permanent dipole interactions occur?

A

between molecules that have large differences in electronegativity between the atoms of that molecule.

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40
Q

What must you note about London dispersion forces and permanent dipole-permanent dipole interactions?

A

London dispersion forces are still present, however, they are weaker than permanent dipole-permanent dipole interactions

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41
Q

What are hydrogen bonds and when do they occur?

A

a special type of permanent dipole-permanent dipole interactions. They are intermolcular forces of attraction only occur in molecules containing a strongly electronegative element bonds to hydrogen i.e.hydrogen bonded to fluorine, nitrogen, oxygen

42
Q

What must you note as well hydrogen bonds what

else is present?

A

london dispersion forces

43
Q

What are hydrogen bonds stronger than?

A

London dispersion forces and permanent dipole-permanent dipole interactions

44
Q

Why does water, ammonia and hydrogen fluorine have higher boiling points than expected ?

A

Due to the presence of intermolecular hydrogen bonds

45
Q

Why does ice freeze in an unusual way?

A

as a result of hydrogen bonding

46
Q

What happens as water is cooled?

A

it starts to contract but a 4 degrees Celsius it starts to expand (this is why water pipes burst when they freeze).

47
Q

Describe the structure of ice and what effect does this have ?

A

is an open lattice due to hydrogen bonds. This makes the ice less dense than liquid water and therefore it can float.

48
Q

What are the 2 types of intramolecular bonds ?

A

polar covalent bonds

non-polar covalent bonds

49
Q

What is the order of bond strength? (weakest to strongest)

A

london dispersion forces
permanent dipole-permanent dipole interactions
hydrogen bonds
Ionic, covalent, metallic

50
Q

When melting/boiling most covalent substances what are the only bonds or forces that are broken?

A

intermolcular forces

51
Q

What structure do metallic and ionic compounds have?

A

giant lattice

52
Q

What are the 3 other types of structures apart from metallic and ionic lattice?

A

monatomic
covalent molecular
covalent network

53
Q

What do monatomic structures consist of?

A

discrete (individual) atoms held together by London dispersion forces

54
Q

What do convalent molecular structures consist of?

A

discrete (individual) molecules held together by London dispersion forces

55
Q

Give 5 elements that have covalent molecular structures and are also considered diatomic?

A 
hydrogen 
nitrogen 
oxygen
fluorine 
chlorine
56
Q

Give 2 examples of elements which have covalent molecular structures and are solid at room temperature?

A

Sulphur

Phosphorus

57
Q

What structure does sulphur have ?

A

a covalent molecular structure in which 8 sulphur atoms are covalently bonded to one another. It is a solid at room temperature.

58
Q

What structure does phosphorus have ?

A

a covalent molecular structure in which 4 phosphorus atoms are covalently bonded to one another. It is a solid at room temperature.

59
Q

What structures do many compounds have and give 4 examples?

A

covalent molecular structures

methane, water, ammonia and carbon dioxide

60
Q

What do covalent network structures consist of?

A

giant lattice of atoms covalently bonded to each other.

61
Q

Give 3 examples of elements with a covalent network structure?

A

boron
silicon
some types of carbon (diamond and graphite)

62
Q

Why is carbon unique?

A

it can exist in 3 forms

63
Q

What are the 3 forms of carbon?

A

fullerenes
carbon diamond
carbon graphite

64
Q

What do fullerenes contain?

A

contain 60-80 carbon atoms

65
Q

Whate structure do fullerenes have?

A

covalent molecular structures

66
Q

Do fullerenes conduct electricity?

A

yes

67
Q

What structure do carbon diamonds have?

A

covalent network structure

68
Q

What is each carbon atom in the diamond covalently bonded to?

A

4 other carbon atoms.

69
Q

What is carbon diamond used for and why?

A

cutting and grinding tools because of its strength

70
Q

What is each carbon atom in graphite covalently bonded to?

A

to another 3 carbon atoms in a network structure

71
Q

What structure does carbon graphite have?

A

covalent network structure

72
Q

What can the free electron from each carbon atom do?

A

move throughout the graphite structure creating delocalised electrons

73
Q

What can the delocalised electrons in carbon graphite move between?

A

the covalent network layers

74
Q

What does the delocalised electrons make carbon graphite?

A

a good conductor of electricity

75
Q

Out of the first 20 elements, what elements are monatomic?

A

Helium
Neon
Argon

76
Q

Out of the first 20 elements, what elements are covalent molecular gas?

A 
hydrogen
nitrogen 
oxygen
fluorine
chlorine
77
Q

Out of the first 20 elements, what elements are covalent molecular soilds?

A

sulfur
phosphorus
fullerenes ( carbon form)

78
Q

Out of the first 20 elements, what elements are covalent network?

A

boron
silicon
carbon graphite
carbon diamond

79
Q

Out of the first 20 elements, what elements are metallic?

A 
Lithium
Beryllium
Sodium
Magnesium 
Aluminium
Potassium 
Calcium
80
Q

Describe the structure for metallic bonding?

A

giant lattice of positively charged ions and delocalised electrons

81
Q

Describe the structure for ionic bonding?

A

giant lattice of oppositely charged ions

82
Q

Describe the structure for monatomic elements?

A

individual atoms held together by weak intermolecular forces (london dispersion forces)

83
Q

Describe the structure for covalent molecular bonding?

A

individual molecules held together by weak intermolecular forces (london dispersion forces)

84
Q

Describe the structure for covalent network bonding?

A

giant lattice of atoms covalently bonded together.

85
Q

What are the 3 properties we look at in terms of bonding and structure?

A

melting/boiling points
solubility
viscosity

86
Q

What does the melting/boiling points depend on?

A

the bonds (forces) that must be broken

87
Q

In terms of melting/boiling points what do metallic/ionic compounds generally have and why?

A

high melting and boiling points due to the large lattice structures that they have.

88
Q

In terms of melting/boiling points what do covalent networks generally have and why?

A

high melting/boiling points because strong covalent bonds have been broken

89
Q

Give 2 examples of covalent network structure and have very high melting/boiling point ?

A

silicon dioxide

silicon carbide

90
Q

In terms of melting/boiling points what do covalent molecular substances depend on ?

A

the type of intermolecular forces holding the molecules together.

91
Q

What is the order of increasing strength of intermolecular forces and what effect does increasing strength have on the melting/boiling point?

A

London dipersion forces
permanent dipole - permanent dipole interactions
hydrogen bonds

melting/boiling point increases

92
Q

In terms of melting/boiling points, what would if a substance only has london dispersion forces between the molecules (give example)?

A

hydrogen gas has a low melting point (-259’c) and boiling point (-253’c).

93
Q

Water has a relatively high melting point for a covalent molecular structure (0’c) and boiling point (100’c), why?

A

it has stronger hydrogen bonds between its molecules

94
Q

What is another way of saying solubility ?

A

miscibility

95
Q

What will polar covalent solvents e.g. water, alcohols dissolve?

A

ionic compounds

polar covalent compounds

96
Q

What will non-polar covalent solvents e.g. hexane, cyclopentane dissolve?

A

candle wax

oil

97
Q

Describe the trend between viscosity of liquids and intermolecular forces?

A

The viscosity of liquids increases as the inermolecular forces increase.

98
Q

what is the trend between the number of hydrogen bonds in a substance and the viscosity?

A

as the number of hydrogen bonds increases the viscosity increases

99
Q

What are ionic compounds soluble in?

A

Water

100
Q

Although most compounds containing metals and nonmetals are ionic what can some actually be ?

A

Covalent

101
Q

What will a low melting boiling point tell you about the bonding ?

A

Covalent bonds

102
Q

Give an example of a compound which would appear to be ionic but it actually covalent ?

A

Titanium chloride

Higher Chemistry Unit 1: Chemical changes and structure (3 decks)

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