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Chemistry > 1 Covalent bonding > Flashcards

1 Covalent bonding Flashcards

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1
Q

What is covalent bonding?

A

It is the strong electrostatic force of attraction between the nuclei of the atoms making up the bond and the shared pair of electrons.

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2
Q

What is covalent bonding in terms of electrostatic attraction?

A

It is the electrostatic attraction between the bonding of electrons and the two nuclei of the atoms bonded together.

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3
Q

How do you draw hydrogen in a dot-and-cross diagram?

A
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4
Q

How do you draw oxygen in a dot-and-cross diagram?

A
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5
Q

How do you draw nitrogen in a dot-and-cross diagram?

A
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6
Q

What is a hydrogen halide?

A

The compound formed between hydrogen and a halogen, with the formula HX where X stands for a halogen atom.

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7
Q

How do you draw water (H2O) in a dot-and-cross diagram?

A
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8
Q

How do you draw ammonia (NH3) in a dot-and-cross diagram?

A
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9
Q

How do you draw carbon dioxide (CO2) in a dot-and-cross diagram?

A
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10
Q

How do you draw methane (CH4) in a dot-and-cross diagram?

A
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11
Q

How do you draw ethane (C2H6) in a dot-and-cross diagram?

A
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12
Q

How do you draw ethene (C2H4) in a dot-and-cross diagram?

A
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13
Q

What are intermolecular forces?

A

The forces that hold molecules together.

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14
Q

Which bonds are weaker than covalent bonds?

A

Intermolecular bonds.

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15
Q

Which bonds are broken when we boil a liquid?

A

The intermolecular bonds are broken - the covalent ones are never broken.

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16
Q

What is a simple molecular structure?

A

When a substance consists of molecules with intermolecular forces of attraction between them.

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17
Q

Are simple molecular structures just solids?

A

No, they are solids, liquids and gases.

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18
Q

Do substances with simple molecular structures have low or high melting and boiling points?

A

They have low melting and boiling points.

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19
Q

Why do simple molecular structures have low melting and boiling points?

A

This is because not much energy is required to break the weak intermolecular forces of attraction between them.

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20
Q

Why do these structures’ melting and boiling points sometimes increase?

A

More energy is required to break the intermolecular forces as the relative molar mass increases. Thus, meaning that the intermolecular forces of attraction must become stronger as relative molecular mass increases.

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21
Q

What is directly proportional to the melting and boiling points of simple molecular structures?

A

The molecular mass.

22
Q

Why do covalent compounds not conduct electricity?

A

This is because the molecules don’t have any overall electrical charge and all the molecules are held tightly in covalent bonds so they are not able to move.

23
Q

What is a giant covalent structure?

A

It is when the atoms are joined up by very strong covalent bonds and they have a variable number of atoms.

24
Q

Why do giant covalent structures have such high melting and boiling points?

A

Because so much energy is needed to break the covalent bonds between the atoms throughout the giant structure

25
Q

What is diamond a form of?

A

Carbon.

26
Q

What kind of structure does diamond have?

A

It is a giant covalent structure, each carbon bonds strongly to four other carbons in a tetrahedral arrangement.

27
Q

Why does diamond have such a high melting and boiling point?

A

It contains carbon - carbon covalent bonds, which extend throughout the whole crystal in three dimensions, and a lot of energy has to be supplied to break them.

28
Q

What has to be broken in giant covalent structures in order to change their state?

A

Their covalent bonds.

29
Q

Why is diamond so hard?

A

A lot of energy needs to be supplied in order to break the covalent bonds in the structure.

30
Q

What are some uses of diamond?

A

Drill bits can be tipped with diamonds for drills used on stone and rocks.

31
Q

Does diamond conduct electricity?

A

No, it doesn’t conduct electricity.

32
Q

Why doesn’t diamond conduct electricity?

A

All of the electrons in the outer shells of the carbon atoms are tightly held in covalent bonds between them. This means that none are free to move around.

33
Q

What are the physical properties of diamond?

A
  • High melting and boiling points.
  • Very hard.
  • Doesn’t conduct electricity.
34
Q

What is graphite a form of?

A

Carbon.

35
Q

What kind of structure does graphite have?

A

It is still a giant covalent structure but the atoms are arranged differently. It has a layer structure. Each layer is strong but the individual layers can be easily separated.

36
Q

Why is graphite soft?

A

This is because the forces in between the strong individual layers are much weaker and not much energy is needed to overcome them. The layers slide over each other and can easily be flaked off.

37
Q

What are some uses of graphite?

A
  • When mixed in clay to make it harder it is used in pencils.
  • Pure graphite can be used as dry lubricant to lubricate locks.
38
Q

Why does graphite have a high melting and boiling point?

A

Even though the forces of attraction between the layers are not that strong; you still have to supply enough energy to break the very strong covalent bonds in each layer. This requires a lot of energy.

39
Q

Does graphite conduct electricity?

A

Yes.

40
Q

Why does graphite conduct electricity?

A

This is because the fourth electron is free to move around in between the layers, meaning it has some delocalised electrons. The movement of these delocalised electrons allows graphite to conduct electricity.

41
Q

What are the physical properties of graphite?

A
  • Soft material.
  • High melting and boiling point.
  • Conducts electricity.
42
Q

What is an allotrope?

A

A different form of the same element.

43
Q

What are the allotropes of carbon?

A
  • Diamond
  • Graphite
  • C60 fullerene
44
Q

What kind of structure does C60 fullerene have?

A

It has a simple molecular structure. It has weak intermolecular forces between them.

45
Q

Does C60 fullerene have a low or high melting and boiling points?

A

It has a lower melting and boiling point than diamond and graphite.

46
Q

What happened when C60 fullerene is melted?

A

Only the relatively weak intermolecular forces of attraction must be broken. This means that it doesn’t require as much energy as breaking all of the strong covalent bonds when diamond and graphite are melted.

47
Q

Is C60 fullerene as hard as diamond?

A

It is not as hard as diamond as it doesn’t take as much energy to break the intermolecular forces of attraction as opposed to the covalent bonds in diamond.

48
Q

Does C60 fullerene conduct electricity?

A

No.

49
Q

Why doesn’t C60 fullerene conduct electricity?

A

The fourth electron on each atom can only jump around within each C60 fullerene molecule - this means that electrons cannot jump from molecule to molecule.

50
Q
A

Chemistry (22 decks)

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