S4.6.7 For the adult
Covalent bonding
A diamond is the hardest natural material. Pencil lead is made of the same atoms. Why is it so soft?
What this chapter teaches
Non-metal atoms share pairs of electrons in covalent bonds. Small molecules have weak forces between them, so they melt at low temperatures and do not conduct. Diamond and graphite are giant structures of carbon with very different properties.
Three questions to ask
There is no one right wording. Listen for the idea.
- How many pairs of electrons does an oxygen atom share in a water molecule?
- Why do substances made of small molecules have low melting points?
- Why is graphite soft and a conductor, while diamond is hard and not?
After the chapter, the learner can
- Draw dot and cross diagrams for water, methane and oxygen
- Compare simple molecules with giant structures such as diamond and graphite
What they copy into their notebook
A covalent bond is a shared pair of electrons. Simple molecules: strong bonds inside, weak forces between, low melting points, no conduction. Diamond: four bonds each, hard. Graphite: layers that slide, and it conducts.