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Group 7: the halogens
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The halogens are reactive non-metals. Unlike Group 1, they get less reactive down the group.
Properties
Exist as diatomic molecules: F2, Cl2, Br2, I2.
Trends
Down the group: melting and boiling points increase, reactivity decreases.
Atoms get bigger, so it is harder to gain an electron (the incoming electron is further from the nucleus).
Atoms get bigger, so it is harder to gain an electron (the incoming electron is further from the nucleus).
Displacement and testing
A more reactive halogen displaces a less reactive one from its salt solution.
chlorine + potassium bromide → potassium chloride + bromine
Test for chlorine: it bleaches damp blue litmus paper (turning it red first).
chlorine + potassium bromide → potassium chloride + bromine
Test for chlorine: it bleaches damp blue litmus paper (turning it red first).
Will iodine displace chlorine from sodium chloride solution?
- Iodine is less reactive than chlorine.
- So no reaction happens.
Answer: No
Halogens are diatomic. Down the group, melting point rises and reactivity falls. A more reactive halogen displaces a less reactive one. Chlorine bleaches damp litmus.
The interactive lesson includes the diagrams for this topic.
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