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Key concepts.2 Flashcards

1
Q

Bonding with ionic compounds

A

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

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2
Q

Structure of ionic compounds

A

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

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3
Q

Properties of ionic compounds

A

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

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4
Q

Ionic compounds solubility in water

A

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

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5
Q

What structure is an ionic compound

A

A lattice

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6
Q

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

A

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

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7
Q

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

A

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

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8
Q

How is a covalent bond formed

A

When a park of electrons is shared between two atoms

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9
Q

Properties of covalent bonds

A
  • 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)

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10
Q

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

A

Unreactive

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11
Q

What are three ways you can represent a covalent bond

A

Dot and cross with shells

Dot and cross without shells

Structural formula

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12
Q

Typical size of atoms

A

1 x 10^-10

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13
Q

Size of simple molecules

A

1 x 10^-9

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14
Q

What does a simple molecule consist of

A

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

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15
Q

Properties of simple molecular substances ususallaee are:

A

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

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16
Q

There are weak attractive forces between molecules called?

A

Intermolecular forces

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17
Q

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

A

Intermolecular forces are overcome

Covalent bonds do not break

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18
Q

Simple molecular substances do not conduct electricity when

A

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

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19
Q

What are simple molecular s solubility

A

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

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20
Q

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

A

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

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21
Q

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

A

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

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22
Q

Giant molecular substances contain

A

Very many atoms rather than just a few

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23
Q

In a giant molecules the atoms are :

A

Joined by strong covalent bonds

Arranged in a regular lattice structure

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24
Q

Giant molecular substances can be :

A
  • non-metal elements such as carbon

* compounds such as silica

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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

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