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Flashcards in Key concepts.2 Deck (91):
1

Bonding with ionic compounds

Ionic bonds are strong electrostatic forces of attraction between oppositely charged ions

Eg sodium reacts with chlorine = NaCl
•electrons transfer from sodium atoms to chlorine atoms
• Na+ ions and Cl- ions form
• Na+ and Cl- ions attract each other

2

Structure of ionic compounds

The ions in an ionic compound form a lattice structure which has :
• a regular arrangement of ions
• ionic bonds between oppositely charged ions

3

Properties of ionic compounds

Usually have high melting point
Hugh boiling point

Solid state at room temperatures

Many strong ionic bonds
Large amounts of energy must be transferred to the lattice structure to break these bonds

4

Ionic compounds solubility in water

Ionic compounds are often soluble in water. They dissolve to form aqueous solutions

5

What structure is an ionic compound

A lattice

6

State why sodium chloride does not conduct electricity when it is in the solid state

The ions are not free to move around in a solid

Although ions are electrically charged, they are held in fixed positions in the lattice structure

7

Explain why sodium chloride does not conduct electricity when it is molten or in aqueous solution

The ions are free to move around when sodium chloride is liquid or when it is dissolved in water. This means they can carry electric charge from place to place


An electric current is a flow of charge. A substance will conduct electricity if :
• it contains charge carriers (such as ions)

These charge carriers are free to move through the substance

8

How is a covalent bond formed

When a park of electrons is shared between two atoms

9

Properties of covalent bonds

• are strong
• form between non-metal atoms
• often produce molecules, which can be elements or compounds

A hydrogen atom can form one covalent bond. Usually for atoms of other non-metals :
•number of bonds = (8-group number)

10

Helium and other elements in group 0 have full outer shells therefore they do not transfer or share electrons so they are

Unreactive

11

What are three ways you can represent a covalent bond

Dot and cross with shells

Dot and cross without shells

Structural formula

12

Typical size of atoms

1 x 10^-10

13

Size of simple molecules

1 x 10^-9

14

What does a simple molecule consist of

Just a few atoms, joined to each other by strong covalent bonds. Simple molecular substance can be :

Non metal elements such as H2 O2 Cl2

Compounds of non-metals such as HCl H2O CH4

15

Properties of simple molecular substances ususallaee are:

Low melting points
Low boiling points

Usually has or liquid at room temperature

Simple molecular substances with relatively large molecules such as wax are in the solid state at room temperature

16

There are weak attractive forces between molecules called?

Intermolecular forces

17

When a simple molecular substance such as oxygen melts or boils :

Intermolecular forces are overcome

Covalent bonds do not break

18

Simple molecular substances do not conduct electricity when

Solid liquid gas because
Molecules are not electrically charged and
Do not contain electrons that are free to move forward

19

What are simple molecular s solubility

Many simple molecular substances are insoluble in water. The intermolecular forces between water and these substances are weaker than those between:
•water molecules
• molecules of the substance itself

20

Simple molecular substance dissolve in water if they can from strong enough intermolecular forces with water molecules :

Hydrogen and oxygen are sparingly soluble (very little dissolves)
Chlorine, carbon dioxide, sulfur dioxide and ammonia are soluble in water
Ethanol and ethanol acid are soluble
Sugar is soluble in water

21

Nitrogen is a colourless, unreactive has at room temperature
Explain why it is suitable for use as an insulator in high-voltage electrical transformers

Nitrogen is unreactive.
Will not react with materials used in transformer
Can insulate parts in transformer because it doesn’t conduct electricity

22

Giant molecular substances contain

Very many atoms rather than just a few

23

In a giant molecules the atoms are :

Joined by strong covalent bonds
Arranged in a regular lattice structure

24

Giant molecular substances can be :

• non-metal elements such as carbon
• compounds such as silica

25

Giant molecular substances usually have :

Hugh melting points
Hugh boiling points

26

What state are giant molecular substances at room temperature

Solid.
A lot of energy must be transferred to break the many strong covalent bonds during meetings and boiling
Insoluble in water

27

What are diamond and graphite both forms of?

Carbon.
Giant molecular substances

28

Diamond

Each atom is bonded to four others
Strong covalent bonds between atoms

29

Graphite

Each atom is bonded to three others

Weak intermolecular forces between layers

Strong covalent bonds between atoms in a layer

30

Explain why graphite conducts electricity whereas diamond does not

Carbon atom can form four covalent bonds. In graphite each carbon atom only forms three covalent bonds, the non-bonding outer electrons become delocalised. This means that they can move through the structure so graphite conducts electricity. Diamond does not have delocalised and so does not conduct

31

Diamond has a rigid lattice structures and strong bonds which make it very

Hard this is why it is useful for cutting tools

32

In graphic the weak intermolecular forces let the layers slide over each other :

This is why it is slippery and useful as a lubricant

33

Metals have delocalised electrons which makes them

Good conductors if electricity

34

Graphemes and fullerenes are forms of

Carbon
Giant molecules

35

What is graphene

A giant molecular substance
Structure of resembles a single layer of graphite

Each carbon atom is covalently bonded to 3 other carbon atoms
It has a regular lattice structure
Interlocking hexagonal rings of carbon atoms

36

Graphene conducts electricity:

The non-bonding outer electrons become Delocalised
They can move through the structure

37

Graphene is very strong and flexible

It contains many strong covalent bonds

38

Grapheme is almost transparent

It’s layers are just one atom thick

39

What’s fullerenes

They resemble a sheet of graphene rolled to form either :

•hollow balls = buckyballs

• hollow tubes = nanotubes

40

What is it called when the grapheme is the road to form hollow balls

Fullerenes called buckyballs

41

What is it called when graphene is rolled to form hollow tubes

Fullerenes, nanotubes

42

Buckminsterfullerene formula

C60

43

C60 has

Carbon atoms arranged in pentagons as well as hexagons

Buckminterfullerene

44

Materials made from buckyballs:

Conduct electricity because I have delocalised electrons

A soft one in the solid-state because they have weak intermolecular forces

45

What is at nanotubes ends

They’re closed ends or open ends

46

How long can nanotubes be

Several millimetres long

47

Properties of nanotubes

Conduct electricity because they have delocalised electrons

Very strong because the structure has many strong covalent bonds

48

What are polymers

Large molecules made from many small molecules called monomers joined together

49

What a polymer molecules described as rather than giant covalent molecules

Macromolecules

50

Polly(Ethene) is not a fullerene:

It is a hydrocarbon (compound of hydrogen and carbon)

51

Most elements are....... and placed in the........ side of the periodic table

Metals

Left

52

Appearance of metals and non-metals

Metals are shiny
Non-metals are dull

53

Electrical property of metals and non-metals

Metals - good
Non-metals - poor

54

Conduction of metals and non-metals

Both Conductors

55

Density of metals + non-metals

Density of metals is High
Density of non metals is low

56

Melting point of non metals and metals

Melting point of metals is high
Melting point of non metals is low

57

Mercury’s is a ........... at room

Liquid

58

Diamond and graphite have a very high melting point even though there non metals

Graphit condycts electricitt

59

Metals are

Malleable - can be pressed into shape without shattering

60

Non metals are

Brittle
In the solid state they shatter when bent or hit

61

Metallic structure and bonding
A metal:

Consists of a giant lattice of positively charged metal ions

Has a ‘sea’ of delocalised electrons

The delocalised electrons come from the outer shells of the atoms

Metallic bonds are strong electrostatic forces between positive metal ions and delocalised electrons

62

Malleable metals
Is a force is applied to a metal:

Layers of positive ions slide over each other

The metal changes shape without shattering

63

Insoluble metals :

Metals are insoluble in water, however some metals do seem to dissolve in water

This is because they react with the water to produce soluble metal hydroxides

This dissolve, exposing more metal to the water

Eg sodium reacts with water forming sodium hydroxide solution and hydrogen :

2Na (s) + 2H2O (l) -> 2NaOH (aq) + H2 (g)

64

Explain why metals are good conductors of electricity

Metals contain delocalised electrons which can move through the structure of the metal

65

What does ductile mean

Can be pulled to make wires without breaking .
The layers of positive ions slide over each other

Eg copper

66

Mercury is a liquid metal at room temperature, state wether it should conduct electricity with a reason

It should because it will have delocalised electrons

67

The formula for a substance can be written as :

A structural formula
A molecular formula
An empirical formula

68

What does the empirical formula show

The simplest whole number ratio of atoms of each element. This does not show how the atoms are arranged or (usually) the actual number of atoms


CH2O

69

What’s the molecular formula

The number of atoms of each element
This does not show how the atoms are arranged

C2H4O2

70

What does the structural formula show

The number of atoms of each element. This gives us an idea of how they are arranged


CH3COOH

71

When you draw a structure you should show all the covalent bonds in the molecule

Some models may not show

The molecules three- dimensional shape
The bonding and non-bonding electrons

72

You can draw ball-and-stick models.

Also make them using plastic modelling kits

73

What do ball-and-stick models show

How each atom is bonded to other atoms

The molecules three-dimensional shape

74

What do ball-and-stick models not show

The bonding and non-bonding electrons

Or each elements chemical symbol

75

What’s another model which is similar to ball-and-stick but more accurate?

Space-filling models

76

Positive and negative of space-filling models

The sizes of atoms are relative to their bonds

You may not be able to see all the atoms in a complex space-filling model

77

Positive and negatives of dot and cross diagrams

Shows symbol for each atom in molecule
Shows how each atom is bonded to other atoms
Non-bonding pairs of electrons in the outer shells are included
Pairs of electrons in each covalent bond are shown by dots and crosses

Doesn’t show three dimensional shape

78

State a limitation of empirical formula

Empirical formula does not show
Actual number of atoms\how the atoms are arranged/three-dimensional shapes of molecules/bonding and non-bonding electrons/sizes of atoms relative to the bonds

79

Limitation of molecular formula

Does not show How the atoms are bonded/three-dimensional shape of molecule/bonding a number ending electrons/size of atoms relative to their bonds

80

Limitations of structural formula

Does not show: three-dimensional shape of molecule/bonding and non-bonding electrons/sizes of atoms relative to the bonds

81

Limitations of drawn formula

Does not show: three-dimensional shape of molecule/bonding and non-bonding electrons/sizes of atoms relative to their bonds

82

Limitations of ball and stick model

Does not show: element symbols/Bonding a non-bonding electrons/sizes of atoms relative to the bonds

83

Limitations of space – filling model does not show

Element symbols/ bonding and non-bonding electrons/ some atoms in complex models

84

Limitations of dot and cross diagram

Does not show:
Three-dimensional shape of molecule / sizes of atoms relative to their bonds

85

Relative formula mass symbol?

Mr

86

To calculate the Mr of a substance you

Add together all the relative atomic masses of all the atoms shown in its formula

87

Relative formula mass of oxygen molecule?

O relative atomic mass = 16
O2 = 16 x 2
= 32

88

What’s is Mr units?

It has no units
Mr values are just numbers

This is because an Mr value is the mass of a molecule or unit of a substance compared with 1/12thxthe mass of a 12C atom. The M in Mr stands for ‘molecular’

You might see or hear the term ‘relative molecular Mass’ this really applies only to covalent substances

89

How do you calculate an empirical formula

Symbol
Mass of each element in g
Ar of each element
Mass/Ar
Divide each by smallest
May need to multiply to rid fractions

90

You can find the molecular formula of a compound from its empirical formula :
If you know it’s relative formula mass Mr

Calculate Mr or empirical formula
Divide Mr of X by answer 1
Multiply each by empirical formula

91

How do you determine the empirical formula experiment

Him