Giant covalent structures
| English | Chinese | Pinyin |
|---|---|---|
| giant covalent | 巨型共价 | jù xíng gòng jià |
| diamond | 金刚石 | jīn gāng shí |
| graphite | 石墨 | shí mò |
| silicon dioxide | 二氧化硅 | èr yǎng huà guī |
| lubricant | 润滑剂 | rùn huá jì |
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:
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?
Four bonds make diamond a rigid, hard lattice.
Because each carbon forms four bonds in a rigid lattice, diamond is extremely ______.
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:
Three bonds leave free electrons; layers slide.
Diamond and graphite are both made of pure carbon.
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