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Chemistry OCR A Level > Topic 2.2.2 > Flashcards

Topic 2.2.2 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 reaction between positive and negative ions

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3
Q

Give 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

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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 shells 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 can not move. When they are in liquid state the ions are mobile and this can freely carry the charge

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8
Q

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

A

They have a 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

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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

They 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

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 point?

A

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

31
Q

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 degrees
•—•—•

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 degrees

35
Q

What is the shape, diagram and bond angle in a shape with 4 bonded pars and 0 lone pairs?

A

Tetrahedral

109.5 degrees

36
Q

What is the shape, diagram and bond angle in a shape with 5 bond pairs and 0 lone pairs?

A

Trigonal bipyramid

90 and 120 degrees

37
Q

What is the shape, diagram and bond angle in a shape with 6 bonded pairs and 0 lone pairs?

A

Octahedral

90 degrees

38
Q

What is the shape, diagram and bond angle in a shape with 3 bond pairs and 1 lone pair?

A

Pyramidal

107 degrees

39
Q

What is the shape, diagram and bond angle in a shape with 2 bonded pairs and two lone pairs?

A

Non linear

104.5 degrees

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 the 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 2 types of intermolecular forces?

A

Hydrogen bonding

Van der Waal’s forces

49
Q

What is the strongest type of intermolecular force?

A

Hydrogen bonding

50
Q

What are the 2 interactions that can be referred as Van der Waal’s forces?

A

Permanent dipole- induced dipole interaction

Permanent dipole- permanent dipole interaction

51
Q

Describe permanent dipole- induced dipole interactions

A

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

52
Q

Describe permanent dipole- permanent dipole interaction

A

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

53
Q

Describe London 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
54
Q

Are London forces greater or smaller in larger molecules?

A

Larger due to more electrons

55
Q

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

A

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

56
Q

What conditions are needed for hydrogen bonding to occur?

A

O-H, N-H and 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 forces of attraction between H nucleus and lone pair of electrons on O,N,F

57
Q

Why is ice less dense than liquid water?

A

In ice, the water molecules are arranged in an orderly pattern. It has an open lattice with hydrogen bonds.

In water, the lattice is collapsed and the molecules are closer together

58
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

Chemistry OCR A Level (7 decks)

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