Chemistry C2

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Atoms that share electrons can also form giant structures or macromolecules. Diamond and graphite (forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures (lattices) of atoms.
All the atoms in these structures are linked to other atoms by strong covalent bonds and so they have very high melting points.
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In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard.
In graphite, each carbon atom bonds to three others, forming layers. The layers are free to slide over each other because there are no covalent bonds between the layers and so graphite is soft and slippery.
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) In graphite, one electron from each carbon atom is delocalised. These delocalised electrons allow graphite to conduct heat and electricity
Carbon can also form fullerenes with different numbers of carbon atoms. Fullerenes can be used for drug delivery into the body, in lubricants, as catalysts, and in nanotubes for reinforcing materials
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Metals conduct heat and electricity because of the delocalised electrons in their structures.
The layers of atoms in metals are able to slide over each other and so metals can be bent and shaped.
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Alloys are usually made from two or more different metals. The different sized atoms of the metals distort the layers in the structure, making it more difficult for them to slide over each other and so make alloys harder than pure metals.
Shape memory alloys can return to their original shape after being deformed, eg Nitinol used in dental braces.
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Other cards in this set

Card 2

Front

In graphite, each carbon atom bonds to three others, forming layers. The layers are free to slide over each other because there are no covalent bonds between the layers and so graphite is soft and slippery.

Back

In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant covalent structure, so diamond is very hard.

Card 3

Front

Carbon can also form fullerenes with different numbers of carbon atoms. Fullerenes can be used for drug delivery into the body, in lubricants, as catalysts, and in nanotubes for reinforcing materials

Back

Preview of the back of card 3

Card 4

Front

The layers of atoms in metals are able to slide over each other and so metals can be bent and shaped.

Back

Preview of the back of card 4

Card 5

Front

Shape memory alloys can return to their original shape after being deformed, eg Nitinol used in dental braces.

Back

Preview of the back of card 5

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