In depth Triple Chemistry (2a)

  • Created by: HarveyCB
  • Created on: 27-09-18 14:24
What are ions
Charged particles
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What can make up ions
Single atoms or groups of atoms
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How are they formed
When electrons are lost or gained
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What ions do metals form
Positive ions
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What ions do non metals form
Negative ions
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How do you know the charge of an ion
It is the same number as the number of electrons lost or gained
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Why are ions formed
Because the element is trying to get a full outer shell
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What is a full outer shell called
A stable electronic structure
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What is the charge of group one ions
1+
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What is the charge of group two ions
2+
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What is the charge of group six ions
2-
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What is the charge of group seven ions
1-
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What is ionic bonding
When oppositely charged electrons are strongly attracted to each other, and are held together by strong electrostatic attraction
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How do you draw an ionic compound
By drawing the atomic structure of the ions within square brackets, labelled with the charge in the top right hand corner. The electrons should be either dots or crosses depending on which element they are originally from
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What is the structure of an ionic compound
Giant ionic lattices (closely packed regular arrangement)
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What are the two ways to draw ionic compounds
Dot and cross diagrams or 3D models
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Evaluate dot and cross diagrams
Show how the compound is formed, but not the structure, or arrangement, ornate relative sizes of the ions
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Evaluate 3D models
Shows the relative sizes, and the regular pattern of an ionic crystal, but you can only see the outer layer
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What is the empirical formula
The formula of an ionic compound which shows how much of each ion you need to have a neutral overall charge
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How do you find the empirical formula from a dot and cross diagram
Count how many of each ion there is
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How do you find the empirical formula from a 3D model
By balancing the charges of the ions you can see in the diagram
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What are the properties of ionic compounds
High melting and boiling points, soluble in water, conductive when melted or dissolved, not when solid
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Why do ionic compounds have high melting and boiling points
It takes a large amount of energy to overcome the strong electrostatic attraction between the ions
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Why are ionic compounds only conductive when dissolved or melted
Because then the ions are free to move and carry a current, but when they're in the solid lattice shape they cannot
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What is covalent bonding
When atoms share electrons to get a full outer shell
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What does a single covalent bond provide
An extra shared electron
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What does a double covalent bond provide
Two extra shared electrons
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What type of atoms form covalent bonds
Non metals
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What are the ways of drawing covalent bonds
Dot and cross diagrams, displayed formulas, 3D models and ball and stick models
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Evaluate dot and cross diagrams for covalent bonding
Shows which element the electrons came from, doesn't show the relative sizes of atoms or how they are arranged
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Evaluate displayed formulas for covalent bonding
Easier to show how atoms are connected in large molecules, doesn't show 3D structure, or which atoms the electrons have come from
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Evaluate 3D models for covalent bonding
Shows the relative sizes of atoms and their arrangements, but can get confusing when it is a large molecule, don't show where the electrons have come from
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Evaluate ball and stick models for covalent bonding
Shows the atoms relative size and their arrangement, and the type of bond (double or single) but can get confusing with large molecules
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How do you find the molecular formula for covalent molecules
Count how many of each atom there is
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What are simple molecules
Molecules made up of only a few atoms joined by covalent bonds
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List 8 examples of simple molecules
Hydrogen, chlorine, hydrogen chloride, methane, ammonia, water, nitrogen and oxygen (you need to learn how to draw all of these)
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Do covalent substances conduct electricity
No, not in any state, as there are no free electrons
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Describe the boiling appoints of covalent substances
Low melting and boiling points, so are mostly gas or liquid at room temperature, as they have very weak intermolecular forces that can be broken easily (with little energy)
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What are the trends in covalent substances melting and boiling points
As they get bigger the intermolecular forces increased and the energy required to break them increases, so the melting and boiling points increase
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What is a polymer made of
Lots of long molecules made up of repeating sections
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How are polymer molecules formed
When lots of small units join together
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Give an example of a molecule and the polymer it forms
Ethene and poly(ethene)
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How do you draw a polymer
By drawing the smallest repeating unit, and putting it in brackets, with bonds extending outside the brackets to join to the next repeating unit. N is put after the brackets to tell you it repeats
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How do you write the molecular formula of a polymer
Write down the molecular formula of the repeating unit in brackets, and outside write n
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Describe the melting and boiling points of polymers
They are higher than simple covalent molecules because the intermolecular forces are stronger, but the melting and boiling points are still lower than ionic or giant covalent compunds'
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What are giant covalent structures
Macromolecules, that are similar to giant ionic structures (lattices) but they are not charged, and are held together by strong covalent bonds
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Describe the melting and boiling points of giant covalent structures
They are very high, as to melt or boil them you need to overcome the strong covalent bonds
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What are allotropes
Different structural forms of the same element in the same physical state
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Name four examples of allotropes of carbon
Diamond, graphite, graphene and fullerenes
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Describe the structure of diamonds
Each carbon atom forms four covalent bonds with other carbon atoms, in a rigid structure
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Why are diamonds melting and boiling points so high
Because the strong covalent bonds require a lot of energy to overcome
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Does diamond conduct electricity
No, as it has no free electrons
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Describe the structure of graphite
Each carbon atom forms three covalent bonds, creating sheets of atoms arranged in hexagons. The layers are held together by weak intermolecular forces
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Why is graphite a good lubricant
Because the layers can mover over each other, making it soft and slippery
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Why are graphites melting and boiling points so high
The covalent bonds in the layers require a lot of energy to be broken
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Can graphite conduct electricity and thermal energy
Yes, as only three of the carbon atoms outer electrons are being used in bonds, so one is delocalised
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What is graphene
A single layer of graphite
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What is the structure of graphite
Carbon atoms joined together in a sheet of hexagons that is one atom thick (a two-dimensional compound)
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What are the properties of graphene
It is very strong, and very light, and can conduct electricity (it has delocalised electrons)
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Where is graphene used
To composite materials to increase strength but not weight, or in electronics (phone screens)
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What are fullerenes
Hollow molecules of carbon, shaped like tubes or balls
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Describe the structure of fullerenes
Carbon atoms arranged into pentagons, hexagons or heptagons that are shaped into a hollow ball or tube
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What is a pentagon
A five sided ring
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What is a hexagon
A six sided ring
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What is a heptagon
A seven sided ring
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Give two examples of fullerenes
Buckminsterfullerene and nanotubes
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What are the properties of nanotubes
They're good conductors of heat and electricity, and have a high length to diameter ratio
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How can fullerenes be used
In medicine, as catalysts, as lubricants, to strengthen materials and in electronics
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What is the molecular formula of buckminsterfullerene
C 60
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Describe the structure of buckminsterfullerene
A hollow sphere made up of 20 hexagons and 12 pentagons
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How are fullerenes used in medicine
To 'cage' other molecules, in order to deliver the drug to a certain area of the body in a highly controlled way
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Why are fullerenes used as catalysts
They have huge surface areas which the catalysts could be attached to
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Why are fullerenes used as lubricants
Because coating moving machine parts in fullerenes drastically reduces friction
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What could fullerenes one day be used to lubricate
Artificial joints
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How are fullerenes used to strengthen materials
The have a high tensile strength, so can be used to strengthen materials without adding much weight
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What does high tensile strength mean
They don't break when stretched
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Give an example of fullerenes being used to strengthen a material
Tennis racket frames
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How are fullerenes used in electronics
Nanotubes conduct electricity, and they're very small, so they can be used in small electrical circuits (like computer/phone microchips)
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How are atoms in a metal arranged
In a regular pattern, in a giant structure
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What word is used to describe the electrons in the outer shells of metals
Delocalised
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What does delocalised mean
The electrons aren't associated with a particular atom or bond- they are free to move through the whole structure
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How are metal atoms held together
There are strong forces of electrostatic attraction between the delocalised electrons and the positive metal ions
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What type of bonding holds metal atoms together
Metallic bonding
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What are some properties of metals
High melting and boiling points, conductive and malleable
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Explain the high melting and boiling points of a metal
The electrostatic forces between the metal atoms and delocalised electrons are very strong, and require a lot of energy to overcome
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Explain why metals are conductive
The delocalised electrons can carry the current or thermal energy throughout the structure, as they are free to move
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Explain why metals are malleable
The atoms in the metal form layers that are able to slide over each other, so the metal can be bent and shaped, as well as hammered or rolled
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What are alloys
A mixture of two or more metals, or, a metal and another element
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Why do we use alloys
Because pure metals aren't right for certain jobs, they are often too soft
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Give some examples of alloys
Gold is mixed with silver and nickel to make it harder. Copper is mixed with zinc to make brass. Bronze is made from copper and tin
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What are some uses for brass
Pipes and musical instruments
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What are some uses for bronze
Sculptures and electrical connections
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Why are alloys harder than pure metals
Different elements have different sized atoms. When another element is mixed with a pure metal, the new atoms distort the layers, making it harder for them to slide over each other
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Other cards in this set

Card 2

Front

What can make up ions

Back

Single atoms or groups of atoms

Card 3

Front

How are they formed

Back

Preview of the front of card 3

Card 4

Front

What ions do metals form

Back

Preview of the front of card 4

Card 5

Front

What ions do non metals form

Back

Preview of the front of card 5
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