Group 7 Element

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  • Created by: Amy
  • Created on: 25-12-12 11:18


The group 7 elements are also known as the halogens. They include fluorine, chlorine, bromine and iodine, which all have seven electrons in their outer shell.

In a displacement reaction, a less reactive element is displaced by a more reactive element.

The group 7 elements are placed in the vertical column second from right in the periodic table.

Chlorine, bromine and iodine are the three Group 7 elements you are likely to see at school. Fluorine is too reactive to keep or produce safely at school. Group 1 elements form salts when they react with metals, which is why they are called the halogens .

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Properties & Uses

Group 7 elementPropertiesTypical use Chlorine Green gas Sterilising water Bromine Orange liquid Making pesticides and plastics Iodine Grey solid Sterilising wounds

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Reactions with Group 1 Element

The group 7 elements react vigorously with group 1 elements such as sodium and potassium. In each case, a metal halide is formed (fluoride, chloride, bromide or iodide).

Group 1\7ChlorineBromineIodine Lithium Lithium chloride - LiCl Lithium bromide - LiBr Lithium iodide - LiI Sodium Sodium chloride - NaCl Sodium bromide - NaBr Sodium iodide - NaI Potassium Potassium chloride - KCl Potassium bromide - KBr Potassium iodide - KI

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Displacement & Reactivity

If a reactive element comes into contact with the compound of a less reactive element a chemical reaction may take place. The less reactive element is removed from the compound and replaced by the more reactive element.

For example, if chlorine is added to a solution of potassium bromide, the bromine is replaced by the chlorine forming potassium chloride. Bromine is formed at the same time and can be detected by its colour.

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Examples of Displacement Reactions

HalogenMetal halideThe most reactive halogenReaction Chlorine Sodium bromide Chlorine Chlorine + sodium bromide → sodium chloride + bromine Chlorine Sodium iodide Chlorine Chlorine + sodium iodide → sodium chloride + iodine Bromine Sodium chloride Chlorine No reaction Bromine Sodium iodide Bromine Bromine + sodium iodide → sodium bromide + iodine Iodine Sodium chloride Chlorine No reaction Iodine Sodium bromide Bromine No reaction

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