GIANT COVALENT STRUCTURES + fullerenes Flashcards
Give examples of giant covalent structures
Examples of giant covalent structures:
Diamond
Graphite
Silicon dioxide
Graphene
Define allotrope
Allotropes are different structural forms of the same element in the same physical state
Examples of allotropes of carbon
Diamond
Graphite
Graphene
Fullerenes
At what state are giant covalent structures at room temperature
Giant covalent molecules are always SOLIDS at room temperature
Explain why giant covalent structures are always solids at room temperatures
Giant covalent molecules are always solids at room temperatures. This is because they have millions of strong covalent bonds which means that they have high melting and boiling points
Describe the melting and boiling points in giant covalent molecules
Giant covalent molecules have high melting and boiling points
From which element is diamond formed
Diamond is formed from the element CARBON
What must happen to melt or boil giant covalent structures
These bonds must be overcome (broken) to melt or boil these substances.
Describe the structure of the giant covalent molecule of diamond
In diamond, each carbon atom forms four strong covalent bonds with four other carbon atoms in a giant covalent structure.
State the properties of diamond
Diamond is very hard (and strong)
Diamond has a very high melting point and boiling point
Diamond does not conduct electricity
Explain why diamond cannot conduct electricity
Diamond cannot conduct electricity because it does not have any delocalised electrons to carry a charge through the giant covalent structure
Explain why diamond has a very high melting and boiling point
This is because diamond has a huge number of strong covalent bonds which must be broken and this takes a lot of energy.
Therefore diamond has a very high melting and boiling point
Explain why diamond is very hard.
In diamond, each carbon atom forms four strong covalent bonds with four other carbon atoms in a giant covalent structure. This makes diamond really hard
What is silicon dioxide also referred as
Silicon dioxide is sometimes called silica or sand
State the elements that silicon dioxide contain
Silicon dioxide contains the elements
Silicon and oxygen (covalently bonded together)
State the properties of silicon dioxide
Silicon dioxide has a very high melting and boiling point.
Silicon dioxide does not conduct electricity
Explain why silicon dioxide does not conduct electricity
Silicon dioxide cannot conduct electricity because there are no free electrons (delocalised electrons) to carry an electrical charge through the giant covalent structure
Explain why silicon dioxide has a very high melting and boiling point
Silicon dioxide has a very high melting and boiling point.
This is because silicon dioxide has a huge number of strong covalent bonds which must be broken and this takes a lot of energy.
State the uses of silicon dioxide
Silicon dioxide is used to make glass and concrete
State the molecular formula for silicon dioxide
Silicon dioxide - SiO2
From which element is graphite formed from
Graphite is formed from the element carbon
State the properties of graphite
Graphite has a high melting and boiling point
Graphite is soft and slippery
Graphite is an excellent conductor of both electricity and heat
Graphite is soft and brittle
Describe the structure of graphite
In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings.
There are no covalent bonds between the layers, only weak intermolecular forces
hexagonal rings - rings of six carbon atoms
Explain why Graphite has a high melting and boiling point
This is because graphite has a huge number of strong covalent bonds which must be broken and this takes a lot of energy.
Therefore graphite has a very high melting and boiling point
Explain why Graphite is soft and slippery
In graphite, each carbon atom forms three covalent bonds with three other carbon atoms, forming layers of hexagonal rings.
There are no covalent bonds between the layers, only weak intermolecular forces, so the layers can slide over each other.
This makes graphite soft and slippery
Is graphite a metal
Graphite is based on the element, carbon, so it is not a metal
Explain why graphite is an excellent conductor of electricity and heat
Graphite has delocalised electrons which can move through the giant covalent structure and carry a charge. The delocalised electrons can also conduct thermal energy (heat)
Explain why graphite can conduct electricity but diamond cannot
Graphite has hexagons of Carbon atoms arranged in layers.
Each Carbon atom forming three strong covalent bonds to its nearest neighbours, (STRUCTURE OF GRAPHITE) AS Carbon atoms have 4 electrons in it’s outer shell, this leaves one free outer electron on each carbon atom in graphite.
The delocalised drift freely along layers, and carry a charge . This enables graphite to conduct electricity.
while
In diamond, each carbon atom forms four strong covalent bonds with four other carbon atoms in a giant covalent structure. (structure of diamond)
ALL the outer shell electrons are involved in covalent bonding therefore there are no free electrons to carry electrical charge through the structure.
Uses of graphite - link these uses to their structures
Graphite is used as a lubricant (in machines) - layers can slide
Graphite is used as electrodes in batteries - conducts electricity
Explain how graphite is similar to metals
Graphite is similar to metals as both graphite and metals have delocalised electrons which move through their structures and carry a charge, making them both good conductors of heat and electricity
How many atoms thick is graphene
Graphene is one atom thick
Uses of graphene
Graphene is used in the electronics industry
Describe the structure of graphene
Graphene is a single layer of graphite.
In graphene, each carbon atom forms three covalent bonds with three other carbon atoms, forming a layer of hexagonal rings.
Describe the properties of graphene
Graphene is an excellent conductor of electricity
Graphene is extremely strong.
Graphene has a high melting point
Explain why graphene has a high melting point
This is because graphene has a huge number of strong covalent bonds which must be broken and this takes a lot of energy.
Therefore graphene has a very high melting and boiling point
Explain why graphene has is very strong
Graphene has many strong covalent bonds. This makes graphene really strong.
Explain why graphene is an excellent conductor of electricity
Graphite has delocalised electrons which can move through the giant covalent structure and carry a charge.
What is a fullerene
Fullerenes are molecules of carbon atoms with hollow shapes.
Describe the structure of fullerenes
The structure of fullerenes is based on hexagonal rings of carbon atoms
but they may also contain rings with five or seven carbon atoms.
What was the first fullerene to be discovered
The first fullerene to be discovered was Buckminsterfullerene (C60)
which has a spherical shape.
What shape is a Buckminsterfullerene molecule?
Buckminsterfullerene (C60)
has a spherical shape.
SPHERICAL
What is the chemical formula for the Buckminsterfullerene molecule
Buckminsterfullerene - C60
From which element are fullerenes formed
Fullerenes are formed from CARBON atoms
Uses of fullerenes
Uses of fullerenes
Pharmaceutical delivery
Lubricants (spherical fullerenes for lubricants)
Catalysts
Hydrogen storage
Anti-oxidants
Reduction of bacterial growth
Strengthening materials (cylindrical fullerenes for strengthening materials)
- drug delivery (round the body)
State the properties of buckminsterfullerene
Low melting and boiling point
Slippery
Soft and brittle
Explain why buckminsterfullerene has a low boiling and melting point
Buckminster fullerene have a simple covalent structure
Simple covalent molecules have weak intermolecular forces. The weak intermolecular forces between the molecules do not require a lot of energy to break, therefore simple covalent molecules have low melting and boiling points.
What type of structure is buckminsterfullerene
Buckminsterfullerene has a simple covalent structure
Explain why Buckminsterfullerene can be used as a lubricant
Buckminsterfullerene can is slippery, it can roll over each other. This makes it good to be used as a lubricant
What can buckminsterfullerene also be referred as
The other names for buckminsterfullerene
Bucky ball
Fullerene
Buckminsterfullerene has ______ _________ atoms joined by _________ bonds
Buckminsterfullerene has sixty carbon atoms joined by covalent bonds.
State a group of fullerenes
Carbon nanotubes - a group of fullerenes
What are carbon nanotubes
Carbon nanotubes are cylindrical fullerenes with very high length to
diameter ratios. Their properties make them useful for
nanotechnology, electronics and materials.
State the properties of carbon nantubes
Carbon nanotube have high tensile strength (can be stretched without breaking)
Carbon nanotubes are excellent conductors of heat and electricity.
State the uses of carbon nanotubes
Carbon nanotubes are used to reinforce composite materials (for example those used in making tennis rackets) due to their high tensile strength
Explain why carbon nanotubes are good conductors of electricity and heat
The bonding of the carbon atoms in carbon nanotubes is like the bonding of the carbon atoms in graphite.
This means that they have delocalised electrons which can move through the structure and carry a charge.
