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A Level Chemistry OCR A > 2.2.2: Bonding and structure > Flashcards

2.2.2: Bonding and structure Flashcards

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1
Q

What are the 3 main types of chemical bonds?

A

● Ionic
● Covalent
● Metallic

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2
Q

Define ionic bonding

A

The electrostatic attraction between positive and negative ions

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3
Q

Given an example of an ionically bonded substance

A

NaCl (Sodium Chloride - salt)

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4
Q

Define covalent bonding

A

Electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

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5
Q

Define metallic bonding

A

Electrostatic attraction between the positive metal ions and the sea of delocalised electrons

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6
Q

Electrons in which shell are represented in a dot and cross diagram?

A

The outer shell

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7
Q

Why does giant ionic lattices conduct electricity when liquid but not when solid?

A

In solid state the ions are in fixed positions and thus cannot move. When they are in liquid state the ions are mobile and thus can freely carry the charge

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8
Q

Giant ionic lattices have high or low melting and boiling point?
Explain your answer

A

They have high melting and boiling point because a large amount of energy is required to overcome the electrostatic bonds

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9
Q

In what type of solvents do ionic lattices dissolve?

A

Polar solvents

E.g water

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10
Q

Why are ionic compounds soluble in water?

A

Water has a polar bond. Hydrogen atoms have a + charge and oxygen atoms have a - charge. These charges are able to attract charged ions

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11
Q

What is it called when atoms are bonded by a single

pair of shared electrons?

A

Single bond

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12
Q

How many covalent bonds does carbon form?

A

4

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13
Q

How many covalent bonds does oxygen form?

A

2

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14
Q

What is a lone pair?

A

Electrons in the outer shell that are not involved in the bonding

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15
Q

What is formed when atoms share two pairs of electrons?

A

Double bond

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16
Q

What is formed when atoms share three pairs of electrons?

A

Triple bond

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17
Q

What is average bond enthalpy?

A

Measure of average energy needed to break the bond

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18
Q

What is a dative covalent bond?

A

A bond where both of the shared electrons are supplied by one atom

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19
Q

How are oxonium ions formed?

A

Formed when acid is added to water, H3O+

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20
Q

What does expansion of the octet mean?

A

When a bonded atom has more than 8 electrons in the outer shell

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21
Q

What are the types of covalent structure?

A

● Simple molecular lattice

● Giant covalent lattice

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22
Q

Describe the bonding in simple molecular structures?

A

Atoms within the same molecule are held by strong covalent bonds and different molecules are held by weak intermolecular forces

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23
Q

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

A

Small amount of energy is enough to overcome the intermolecular forces

24
Q

Can simple molecular structures conduct electricity?

A

No, they are non conductors.

25
Q

Why do simple molecular structures not conduct electricity?

A

The have no free charged particles to move around

26
Q

Simple molecular structures dissolve in what type of solvent?

A

Non polar solvents

27
Q

Give examples of giant covalent structures

A

● Diamond
● Graphite
● Silicon dioxide, SiO2

28
Q

List some properties of giant covalent structures (3 marks)

A

● High melting and boiling point
● Non conductors of electricity, except graphite
● Insoluble in polar and non polar solvents

29
Q

How does graphite conduct electricity?

A

Delocalised electrons present between the layers are able to move freely carrying the charge

30
Q

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

A

Strong covalent bonds within the molecules need to be broken which requires a lot of energy

31
Q

Draw and describe the structure of a diamond

A

3D tetrahedral structure of C atoms, with each C atom

bonded to four others

32
Q

What does the shape of a molecule depend on?

A

Number of electron pairs in the outer shell
Number of these electrons which are bonded and
lone pairs

33
Q

What is the shape, diagram and bond angle in a shape with 2

bonded pairs and 0 lone pairs?

A

Linear

180°

34
Q

What is the shape, diagram and bond angle in a shape with 3

bonding pairs and 0 lone pairs?

A

Trigonal planar

120°

35
Q

What is the shape, diagram and bond angle in a shape with 4

bonded pairs and 0 lone pairs?

A

Tetrahedral

109.5°

36
Q

What is the shape, diagram and bond angle in a shape with 5

bonded pairs and 0 lone pairs?

A

Trigonal bipyramidal

90° and 120°

37
Q

What is the shape, diagram and bond angle in a shape with 6

bonded pairs and 0 lone pairs?

A

Octahedral

90°

38
Q

What is the shape, diagram and bond angle in a shape with 3

bonded pairs and 1 lone pairs?

A

Pyramidal

107°

39
Q

What is the shape, diagram and bond angle in a shape with 2

bonded pairs and 2 lone pairs?

A

Non linear

104.5°

40
Q

By how many degrees does each lone pair reduce

the bond angle?

A

2.5 degrees

41
Q

Define electronegativity

A

The ability of an atom to attract the pair
of electrons (the electron density) in a
covalent bond

42
Q

In which direction of the periodic table does electronegativity
increase?

A

Top right, towards fluorine

43
Q

What does it mean when the bond is non-polar?

A

The electrons in the bond are evenly

distributed

44
Q

What is the most electronegative element?

A

Fluorine

45
Q

How is a polar bond formed?

A

Bonding atoms have different

electronegativities

46
Q

Why is H2O polar, whereas CO2 is non polar?

A

CO2 is a symmetrical molecule, so there is no overall dipole

47
Q

What is meant by intermolecular force?

A

Attractive force between neighbouring

molecules

48
Q

What are the 3 types of intermolecular forces?

in order of strength

A

hydrogen bonding
permanent dipole-dipole forces
induced dipole-dipole interactions (london dispersion forces)

49
Q

What is the strongest type of intermolecular force?

A

hydrogen bonding

50
Q

Describe permanent dipole- induced dipole interactions

A

When a molecule with a permanent dipole is
close to other non polar molecules it causes
the non polar molecule to become slightly
polar leading to attraction

51
Q

Describe permanent dipole- permanent dipole interactions

A

Some molecules with polar bonds have
permanent dipoles → forces of attraction
between those dipoles and those of
neighbouring molecules

52
Q

Describe London dispersion forces

A

● London forces are caused by random movements of
electrons
● This leads to instantaneous dipoles
● Instantaneous dipole induces a dipole in nearby
molecules
● Induced dipoles attract one another

53
Q

Are London dispersion forces greater in smaller or larger molecules?

A

Larger due to more electrons

54
Q

Does boiling point increase or decrease down the noble gas group? Why?

A

Boiling point increases because the
number of electrons increases and
hence the strength of London forces also
increases

55
Q

What conditions are needed for hydrogen bonding to occur?

A

O-H, N-H or F-H bond, lone pair of electrons on O, F, N
Because O, N and F are highly electronegative, H nucleus is left exposed
Strong force of attraction between H nucleus and lone pair of electrons on O, N, F

56
Q

Why is ice less dense than liquid water?

A

● In ice, the water molecules are arranged in a
orderly pattern. It has an open lattice with
hydrogen bonds.
● In water, the lattice is collapsed and the
molecules are closer together.

57
Q

Why does water have a melting/ boiling point higher than

expected?

A

Hydrogen bonds are stronger than other
intermolecular forces so extra strength is
required to overcome the forces

A Level Chemistry OCR A (38 decks)

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