Giant covalent structures
Introduced| English | Meaning |
|---|---|
| giant covalent/ˈdʒaɪənt ˈkəʊvələnt/ | Describing a structure with many atoms joined in an extended network by covalent bonds. |
| diamond/ˈdaɪəmənd/ | A form of carbon in which each atom bonds to four others in a three-dimensional giant covalent structure. |
| graphite/ˈɡræfaɪt/ | A form of carbon with layers of bonded atoms, used in pencils and able to conduct electricity through delocalised electrons. |
| silicon dioxide/ˈsɪlɪkən daɪˈɒksaɪd/ | The compound SiO2, whose common solid forms contain a network of silicon and oxygen atoms joined by covalent bonds. |
| lubricant/ˈluːbrɪkənt/ | A substance applied between moving surfaces to reduce friction and wear. |
Covalent giants
- Not all covalent substances are small molecules. Some are vast networks of atoms — giant covalent 巨型共价 structures.
- Their endless web of strong bonds gives remarkable properties.
Giant covalent lab
Compare giant covalent structures by bonding and properties.
A giant covalent structure has:
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It is a continuous network of covalent bonds.
Giant covalent structures
- A giant covalent structure has millions of atoms joined by covalent bonds in a continuous network.
- Examples: diamond 金刚石, graphite 石墨 and silicon dioxide 二氧化硅 (sand).
In a covalent bond atoms share pairs of electrons so each reaches a full outer shell
In diamond, each carbon atom is bonded to how many others?
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Four bonds make diamond a rigid, hard lattice.
Because each carbon forms four bonds in a rigid lattice, diamond is extremely ______.
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The rigid 3D network makes diamond hard.
Diamond
- In diamond, each carbon atom bonds to four others in a rigid 3D lattice.
- This makes diamond extremely hard with a very high melting point.
Graphite can conduct electricity and is soft because it has:
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Three bonds leave free electrons; layers slide.
Diamond and graphite are both made of pure carbon.
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Different bonding arrangements give different properties.
Graphite
- In graphite, each carbon bonds to three others, forming layers that can slide.
- This makes graphite soft (a lubricant 润滑剂) and able to conduct electricity (free electrons between layers).
Diamond and graphite are both pure carbon: diamond's 3D lattice is hard, graphite's layers slide and conduct
Diamond and graphite are both pure carbon. Same element, but a different arrangement of bonds gives completely different properties — hard and non-conducting (diamond) vs soft and conducting (graphite).
You've got it
- giant covalent structures are huge networks of covalently bonded atoms (high melting points)
- diamond: 4 bonds per carbon → very hard, doesn't conduct
- graphite: 3 bonds, sliding layers → soft and conducts electricity