Group 7- The Halogens

7 electrons in their outer shell, they need one more for a full outermost shell and they are really reactive
At room temperature:
1. Chlorine is fairly reactive and poisonous, it is a green gas which is very dense
2. Bromine is also a dense halogen; it is an orange liquid which is poisonous
3. Iodine is dark grey, and is a crystalline solid
Halogens react with most metals to form salts called metal halides
Halogens also react with oxygen to form Hydrogen Halides
1. e.g. chlorine reacts with hydrogen to form hydrogen chloride gas
  1. then the hydrogen chloride gas can be dissolved in water to form hydrochloric acid
2. They are soluble in water and form acidic solutions
Group 1 form alkaline solutions, Group 7 form acidic solutions
The closer to the top in group 7, the more reactive and the further down the least reactive. This is because near the top the electrons are closer to the nucleus. This means that the force is greater and attracts extra electrons more strongly
When halides dissolve it water, the electrons are more free to react
If a more reactive halogen reacts with a less reactive one in a solution then the more reactive will displace the less reactive halogen. E.g. Lithium would displace Potassium

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