C3.7 - Giant covalent structures Flashcards
What is diamond a form of?
Diamond is a form of the element carbon
What is the hardest known natural substance?
The hardest known natural substance is diamond
How can artificial diamonds be made?
Artificial diamonds can be made by heating pure carbon to very high temperatures under enormous pressures
Artificial diamonds can be made by heating pure carbon to very high temperatures under enormous pressures.
What happens to ‘industrial diamonds’ made like this?
‘Industrial diamonds’ made like this are embedded in the drills used by oil companies
Artificial diamonds can be made by heating pure carbon to very high temperatures under enormous pressures.
‘Industrial diamonds’ made like this are embedded in the drills used by oil companies.
What do the oil companies have to do?
The oil companies have to drill through layers of rock to get to the crude oil deep underground
Giant covalent structures
Giant covalent structures are huge 3D networks of covalently bonded atoms
Why do diamonds make beautiful jewellery?
Diamonds make beautiful jewellery, because they are:
- Hard
- Shiny
- Transparent
How are giant covalent structures held together?
Giant covalent structures are held together by covalent bonds throughout the lattice
As well as diamond, what also have giant covalent structures?
As well as diamond:
1. Graphite
2. Silicon dioxide (silica)
also have giant covalent structures
What does having a giant covalent structure give substances?
Having a giant covalent structure gives substances some very special properties, they:
- Have very high melting points and boiling points
- Are insoluble in water
- Are hard and do not conduct electricity, apart from graphite
Having a giant covalent structure gives substances some very special properties, they have very high melting points and boiling points, are insoluble in water and are hard and do not conduct electricity, apart from graphite.
Example
For example, diamond:
- Is exceptionally hard
- Has a boiling point of 4827 degrees Celsius
In diamond, each carbon atom does what?
In diamond, each carbon atom forms 4 strong covalent bonds
What is carbon not always found as?
Carbon is not always found as diamonds
Carbon is not always found as diamonds.
What is another form of carbon?
Another form of carbon is graphite
In graphite, the carbon atoms are only what?
In graphite, the carbon atoms are only bonded to 3 other carbon atoms
In graphite, the carbon atoms are only bonded to 3 other carbon atoms.
They form hexagons, which are arranged in giant layers.
What is there between the layers?
There no covalent bonds between the layers, only weak intermolecular forces
In graphite, the carbon atoms are only bonded to 3 other carbon atoms.
They form hexagons, which are arranged in giant layers.
There no covalent bonds between the layers, only weak intermolecular forces, so what can happen?
There no covalent bonds between the layers, only weak intermolecular forces, so the layers can slide over each other quite easily
In graphite, the carbon atoms are only bonded to 3 other carbon atoms.
They form hexagons, which are arranged in giant layers.
There no covalent bonds between the layers, only weak intermolecular forces, so the layers can slide over each other quite easily.
What does this make graphite?
This makes graphite a soft material that feels slippery to the touch
What do carbon atoms have in their outer shell available for bonding?
Carbon atoms have 4 electrons in their outer shell available for bonding
Carbon atoms have 4 electrons in their outer shell available for bonding.
What does this leave in graphite?
This leaves one spare outer electron on each carbon atom in graphite
Carbon atoms have 4 electrons in their outer shell available for bonding.
This leaves one spare outer electron on each carbon atom in graphite.
What can these mobile electrons do?
These mobile electrons can move freely along the layers of carbon atoms
What are the mobile electrons found in graphite called?
The mobile electrons found in graphite are called delocalised electrons
Delocalised electron
A delocalised electron is a bonding electron that is no longer associated with any one particular atom
Carbon atoms have 4 electrons in their outer shell available for bonding.
This leaves one spare outer electron on each carbon atom in graphite.
These mobile electrons can move freely along the layers of carbon atoms.
The mobile electrons found in graphite are called delocalised electrons.
They no longer what?
The delocalised electrons no longer belong to any one particular carbon atom
What allows graphite to conduct electricity?
The delocalised electrons allow graphite to conduct electricity
The delocalised electrons allow graphite to conduct electricity.
What will the electrons do, when put into an electrical circuit?
When put into an electrical circuit, the electrons will drift away from:
- The negative terminal of a battery
- Towards its positive terminal
What can diamond and other covalently-bonded substances not do?
- Diamond
- Other covalently-bonded substances
cannot conduct electricity
Why can diamond other covalently-bonded substances not conduct electricity?
- Diamond
- Other covalently-bonded substances
cannot conduct electricity, because their atoms have no free electrons
What is graphite excellent at?
Graphite is an excellent conductor of thermal energy
Why is graphite an excellent conductor of thermal energy?
Graphite is an excellent conductor of thermal energy, because as more energy is transferred to the delocalised electrons, they:
- Move around faster
- Rapidly transfer the energy along the layers in the graphite
What happens when you write with a pencil?
When you write with a pencil, some layers of carbon atoms from the graphite:
- Slide off the ‘lead’
- Are left on the paper
Diamond is a form of the element carbon, the same element contained in what?
Diamond is a form of the element carbon, the same element contained in pencil leads
Many covalently bonded substances are made up of individual molecules.
However, some substances, such as diamond, form very different structures.
These do not have what?
These do not have relatively small numbers of atoms arranged in simple molecules
Many covalently bonded substances are made up of individual molecules.
However, some substances, such as diamond, form very different structures.
These do not have relatively small numbers of atoms arranged in simple molecules.
They form what?
They form huge networks of atoms held together by strong covalent bonds in giant covalent structures
In diamond, each carbon atom forms 4 strong covalent bonds, arranged in a what?
In diamond, each carbon atom forms 4 strong covalent bonds, arranged in a perfectly symmetrical giant lattice
Carbon is not always found as diamonds.
Another form of carbon is graphite, the form of carbon used in what?
Another form of carbon is graphite, the form of carbon used in pencil lead
In graphite, the carbon atoms are only bonded to 3 other carbon atoms.
They form what?
The carbon atoms form hexagons
In graphite, the carbon atoms are only bonded to 3 other carbon atoms.
The carbon atoms form hexagons, which are what?
The carbon atoms form hexagons, which are arranged in giant layers
Carbon atoms have 4 electrons in their outer shell available for bonding.
This leaves one spare outer electron on each carbon atom in graphite.
These mobile electrons can move freely along the layers of carbon atoms.
The mobile electrons found in graphite are called delocalised electrons.
The delocalised electrons no longer belong to any 1
one particular carbon atom.
They behave rather like what?
The delocalised electrons behave rather like the electrons in a metallic structure
Diamond and other covalently-bonded substances cannot conduct electricity, because their atoms have no free electrons, because what?
- Diamond
- Other covalently-bonded substances
cannot conduct electricity, because their atoms have no free electrons, because all their outer shell electrons are involved in covalent bonding
