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A-level Chemistry > Covalent bonding > Flashcards

Covalent bonding Flashcards

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1
Q

What is a covalent bond?

A

The strong electrostatic attraction between two nuclei and the shared pair of electrons between them.

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2
Q

What is a dative covalent bond?

A

When the pair of electrons shared by 2 atoms in a covalent bond comes from the same arom

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3
Q

what is the average bond enthalpy?

A

a measure of the strength of a covalent bond. The stronger the bond, the higher its value.

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4
Q

Why don’t covalently bonded molecules conduct electricity?

A

Because there’s no delocalised electrons available to carry a charge

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5
Q

Describe the solubility of covalent molecules

A

They tend to be more soluble in organic solvents than in water- some are hydrolysed

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6
Q

Why do covalent molecules have low boiling points?

A

Because the intermolecular forces between molecules are weak and don’t require a large amount of energy in order to be overcome

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7
Q

When does the intermolecular forces between covalent molecules increase?

A

when the molecules gain more electrons because then there’s a stronger force of attraction between the electrons and the nucleus

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8
Q

What is electronegativity?

A

A measure of how strongly atoms can attract shared electrons

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9
Q

the smaller the distance between the nucleus and the outer electrons, the ….

A

stronger the force of attraction between the shared electrons and the nucleus

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10
Q

the greater the distance between the nucleus and the outer electrons, the ….

A

weaker the force of attraction between the shared electrons and the nucleus

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11
Q

the greater the charge of the nucleus [the more protons it has] ….

A

the stronger the attraction between the nucleus and the shared electrons

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12
Q

is aluminium chloride a covalent molecule or an ionic compound?

A

An covalent molecule

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13
Q

Draw the covalent bonding shown in O2

A

Answer in book

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14
Q

Draw the covalent bonding shown in CO2

A

Answer in book

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15
Q

Draw the covalent bonding shown in HCl

A

Answer in book

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16
Q

Draw the covalent bonding shown in H2O

A

Answer in book

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17
Q

Draw the covalent bonding shown in NH4+

A

Answer in book

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18
Q

Draw the covalent bonding shown in CO

A

Answer in book

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19
Q

Draw the covalent bonding shown in H3O+

A

Answer in book

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20
Q

How many electrons does boron have on its outer shell after covalently bonding?

A

6

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21
Q

What is a lone pair of electrons?

A

2 electrons that aren’t used in bonding

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22
Q

What is phosphorus pentachloride?

A

Where the phosphorus atom has formed 5 covalent bonds so that it has a total of 10 electrons on its outer shell. This is because of phosphorus’ 3d subshell and as it uses all 5 of its outer electron to covalently bond, it end up with 10 electrons on its outer shell. This is called the expansion of the octet

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23
Q

Why can’t atoms in period 1 and 2 undergo the expansion of the octet?

A

Because these elements don’t have a d subshell

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24
Q

Why is aluminium chloride covalently bonded instead of ionically?

A
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25
Q

What is electron pair repulsion theory?

A

The idea that the shape of the molecule is determined by the electron pairs surrounding the central atom

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26
Q

What do solid lines tell you?

A

That bonds lie on the plane of the screen or page

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27
Q

What do solid wedges tell you?

A

That bonds are coming out of the plane of the page

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28
Q

What does a dotted wedge tell you?

A

That a bond is projecting back behind the plane of the page

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29
Q

What structure does beryllium chloride have?

A

A linear one., Or a straight line

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30
Q

When you have a central atom with with 3 pairs of bonding electrons around it what is this called?(as long as the central atom has no lone pairs of electrons)

A

Trigonal planar

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31
Q

What does planar mean?

A

Flat

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32
Q

What shape of molecule is formed when a central atom has 4 pairs of bonding electrons surrounding it?

A

A tetrahedral molecule e.g methane

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33
Q

What degrees are all the angles in tetrahedral molecules?

A

109.5 degrees

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34
Q

What shape is the central atom if it has 5 pairs of bonding electrons surrounding it?

A

Two of the bonding pairs move to opposite sides of the molecule. The other 3 bonding pairs take up a central position lying on the same plane and they spread themselves out as far as they can. This forms a shape called a trigonal bipyramidal

35
Q

Describe the octahedral shape of a molecule

A

The central atom is surrounded by 6 bonding pairs

36
Q

Do dative bond affect the shape of molecules?

A

No.because dative bonds act in the same way as covalent bonds

37
Q

Do lone pairs repel more strongly than bonding pairs?

A

Yes. This extra repulsion decreases other bond angles by 2.5 degrees

38
Q

What happens to the lone pair in the ammonium ion?

A

It forms a dative covalent bond, which has the same level of repulsions as a covalent bond

39
Q

How many lone pairs does water have?

A
  1. It’s shape is based on the tetrahedron And is v shaped
40
Q

How does a short bond affect the bond enthalpy?

A

The shorter the bond, the higher the bond enthalpy

41
Q

What do lone pairs do to bonding pairs?

A

Push them closer together because bond pairs repel lone pairs more than they repel each other

42
Q

If there’s 2 bonding pairs and no lone pairs, what shape will the molecule be?

A

Linear

43
Q

If there’s 2 bonding pairs and no lone pairs, what will the bond angle be?

A

180 degrees

44
Q

What is an example of a molecule with 2 bond pairs and no lone pairs?

A

BeCl2

45
Q

If there’s 3 bonding pairs and no lone pairs, what shape will the molecule be?

A

Trigonal planar

46
Q

If there’s 3 bonding pairs and no lone pairs, what will the bond angle be?

A

120 degrees

47
Q

What is an example of a molecule with 3 bonding pairs and no lone pairs?

A

BF3

48
Q

If there’s 4 bonding pairs and no lone pairs, what shape will the molecule be?

A

Tetrahedral

49
Q

If there’s 4 bonding pairs and no lone pairs, what will the bond angle be?

A

109.5 degrees

50
Q

What’s an example of a molecule with 4 bonding pairs and no lone pairs?

A

CH4

51
Q

Is a tetrahedral 2D or 3D?

A

3D

52
Q

If there’s 5 bonding pairs and no lone pairs, what shape will the molecule be?

A

Trigonal bipyramidal

53
Q

If there’s 5 bonding pairs and no lone pairs, what will the bond angles be?

A

One will be 90 degrees and one will be 120 degrees

54
Q

What is an example of a molecule with 5 bonding pairs and no lone pairs?

A

PCl5

55
Q

If there’s 6 bonding pairs and no lone pairs, what shape will the molecule be?

A

An octahedral

56
Q

If there’s 6 bonding pairs and no lone pairs, what will the bond angle be?

A

90 degrees

57
Q

What is an example of a molecule with 6 bonding pairs and no lone pairs?

A

SF6

58
Q

If there’s 3 bonding pairs and 1 lone pair, what shape will the molecule be?

A

Trigonal pyramidal

59
Q

If there’s 3 bonding pairs and 1 lone pair, what will the bond angle be?

A

107 degrees

60
Q

What’s an example of a molecule with 3 bonding pairs and one lone pair?

A

NH3

61
Q

If there’s 2 bonding pairs and 2 lone pairs, what shape will the molecule be?

A

Bent

62
Q

If there’s 2 bonding pairs and 2 lone pairs, what will the bond angle be?

A

104.5 degrees

63
Q

What’s an example of a molecule with 2 bonding pairs and 2 lone pairs?

A

H2O

64
Q

If there’s 3 bonding pairs and 2 lone pairs, what shape will the molecule be?

A

A distorted T

65
Q

If there’s 3 bonding pairs and 2 lone pairs, what will the bond angle be?

A

87.5 degrees

66
Q

What is an example of a molecule with 3 bonding pairs and 2 lone pairs?

A

ClF3

67
Q

If there’s 4 bonding pairs and 1 lone pair, what shape will the molecule be?

A

Seesaw

68
Q

If there’s 4 bonding pairs and 1 lone pair, what will the bond angles be?

A

87 degrees and 102 degrees

69
Q

If there’s 5 bonding pairs and 1 lone pair, what shape will the molecule be?

A

Square pyramidal

70
Q

What’s an example of a molecule with 4 bonding pairs and 1 lone pair?

A

SF4

71
Q

If there’s 5 bonding pairs and 1 lone pair, what will the bond angles be?

A

90 degrees and 81.9 degrees

72
Q

What’s an example of a molecule with 5 bonding pairs and 1 lone pair?

A

IF5

73
Q

If there’s 4 bonding pairs and 2 lone pairs, what will the shape of the molecule be?

A

Square planar

74
Q

If there’s 4 bonding pairs and 2 lone pairs, what will the bond angle be?

A

90 degrees

75
Q

What’s an example of a molecule with 4 bonding pairs and 2 lone pairs?

A

XeF4

76
Q

Why does graphite have a high melting point?

A

Because a lot of energy is required to overcome its strong covalent bonds

77
Q

Why does graphite have a low density and why is it lightweight?

A

Because the layers are very far apart in comparison to the covalent bond lengths.

78
Q

Is graphite soluble or insoluble?

A

Insoluble because of its strong covalent bonds

79
Q

What shape is diamond ?

A

A tetrahedral

80
Q

What does diamonds tightly packed arrangement allow it to do?

A

Conduct heat

81
Q

What can diamond be cut into?

A

Gemstones

82
Q

Is diamond soluble or insoluble?

A

Insoluble

83
Q

Describe graphene

A

1 layer of graphite, 1 atom thick, hexagonal carbon rings

84
Q

What can graphene be used in ?

A

Electronics

A-level Chemistry (19 decks)

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