Structure & Bonding of Carbon (AQA GCSE Combined Science: Trilogy: Chemistry): Flashcards
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Describe the structure of diamond.
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Describe the structure of diamond.
Diamond is a giant covalent structure in which each carbon atom is bonded to four other carbon atoms by strong covalent bonds in a tetrahedral arrangement. There are no intermolecular forces. Diamond is an allotrope of carbon.
Why does diamond not conduct electricity?
In diamond, all four outer-shell electrons of each carbon atom are used in covalent bonds. There are no free electrons or free ions available to move and carry a charge, so diamond cannot conduct electricity in any state.
In diamond, each carbon atom forms ________ covalent bonds arranged in a ________ shape.
In diamond, each carbon atom forms four covalent bonds arranged in a tetrahedral shape.
True or False?
Diamond is made up of four carbon atoms bonded together.
False.
Diamond has a giant lattice structure with a huge number of carbon atoms. Each carbon atom is bonded to four other carbon atoms by strong covalent bonds. There are not just four carbon atoms in total.
Why is diamond an extremely hard substance?
Every carbon atom in diamond is bonded to four others by strong covalent bonds throughout the giant lattice. This rigid, extensively cross-linked network resists deformation in all directions, making diamond very hard.
True or False?
Diamond is the hardest naturally occurring mineral, which means it is also the strongest.
False.
Hard and strong have different meanings. Hard means resistant to scratching (the opposite is soft). Diamond is hard but brittle: it can be shattered by a sharp blow. It is not necessarily the strongest material.
Describe the structure of graphite and explain why it can conduct electricity.
In graphite, each carbon atom forms three covalent bonds to other carbons, creating layers of hexagons. This leaves one delocalised electron per carbon atom, which is free to move through the structure and carry charge, allowing graphite to conduct electricity. The layers are held together by weak intermolecular forces.
Why are the layers in graphite able to slide over each other, and what property does this give?
The covalent bonds within each layer are strong, but the intermolecular forces between the layers are weak. The layers can therefore slide over each other, making graphite soft and slippery. This makes it useful as a lubricant.
In graphite, each carbon atom forms ________ covalent bonds, leaving ________ delocalised electron per atom. The layers of carbon are held together by weak ________.
In graphite, each carbon atom forms three covalent bonds, leaving one delocalised electron per atom. The layers of carbon are held together by weak intermolecular forces.
True or False?
Graphite conducts electricity because ions or carbon atoms are free to move through the structure.
False.
Graphite conducts electricity because it has delocalised electrons that carry electrical charge through the structure. Ions and atoms cannot move through graphite: only the delocalised electrons are mobile.
State two uses of graphite linked to its properties.
Lubricant: the weak intermolecular forces between layers allow them to slide, making graphite slippery.
Electrodes in electrolysis: graphite conducts electricity and is inert (does not react with the electrolyte).
True or False?
Diamond, graphite and graphene all contain carbon atoms arranged in hexagonal rings.
False.
Only graphite and graphene contain atoms arranged in hexagonal rings. In diamond, each carbon forms a 3D tetrahedral lattice: there are no hexagonal rings.
Describe the structure of graphene.
Graphene is a single layer of carbon atoms arranged in hexagonal rings, only one atom thick (essentially a 2D molecule). Each carbon forms three covalent bonds, leaving one delocalised electron per atom. These delocalised electrons carry electrical charge through the structure, allowing graphene to conduct electricity.
State four properties of graphene.
Graphene is:
extremely strong yet very light
a conductor of heat and electricity (due to delocalised electrons),
transparent to visible light
flexible asits covalent bonds can bend without breaking.
In graphene and nanotubes, each carbon atom forms ________ covalent bonds. One electron from each atom becomes ________, allowing these electrons to carry ________ through the structure.
In graphene and nanotubes, each carbon atom forms three covalent bonds. One electron from each atom becomes delocalised, allowing these electrons to carry electrical charge through the structure.
True or False?
Buckminsterfullerene (C60) contains 60 carbon atoms arranged in hexagonal rings only.
False.
C60 contains 20 hexagons and 12 pentagons, giving it a hollow sphere shape like a football. Fullerenes can include five- and seven-membered rings, not just hexagons.
State two uses of fullerenes or carbon nanotubes and link each to a property.
Electronics: fullerenes and nanotubes conduct electricity (delocalised electrons), making them useful in electronic components.
Drug delivery: the hollow cage structure can trap drug molecules, carrying them to specific targets in the body.
Explain in three steps why carbon nanotubes can conduct electricity.
Each carbon atom in a nanotube forms three covalent bonds.
This means one electron from each carbon atom is delocalised.
These delocalised electrons carry electrical charge through the nanotube.
(Note: mark schemes require "through" not "throughout".)
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