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Science

The Halogens

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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 removed and replaced by a more reactive element.

Halogens

The Periodic Table, with group 7 highlighted

The periodic table

Group 7, also known as the halogens, includes fluorine, chlorine, bromine and iodine. Chlorine is used to sterilise the drinking water supply and in the manufacture of many important chemicals such as pesticides and plastics. Iodine can be used to sterilise wounds.

An important compound of chlorine is sodium chloride or common salt. It's used to preserve food, as flavouring and to manufacture chlorine.

The properties of the halogens

The halogens have similar properties because they all have seven electrons in the outer shell. They all react very vigorously with alkali metals.

HalogenAppearanceReaction with sodiumReactivity
Chlorinepale green gassodium + chlorine → sodium chlorideextremely reactive
Bromineorange liquidsodium + bromine → sodium bromidevery reactive
Iodinegrey solidsodium + iodine → sodium iodidereactive

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