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Chemistry - The Halogens

The Halogens are a group of fine elements:

Fluorine

Chlorine

Bromine

Iodine

Astatine

They are all very reactive and poisonous and together form group 7 of the periodic table.

Fluorine

Fluorine is a poisonous gas, it is extracted from the mineral fluorite. Fluorides, which are non-poisonous compounds of fluorine, are added to toothpaste and drinking water to prevent tooth decay.

Fluorine is also combined with carbon to make compounds called fluorocarbons. An example is PTFE (polytetrafluoroethene), which is used as a non-stick coating for pans and skis.

 

Chlorine

On its own, chlorine is a poisonous gas. It is very reactive and only occurs naturally in compounds such as sodium chloride.

Chlorine is used; as a disinfectant; to make hydrochloric acid and PVC (polyvinylchloride) plastic.

Compounds of chlorine have many uses, sodium hypochlorite, for example, is used to make household bleach.

 

Bromine

Bromine is a foul-smelling, brown liquid, traces of bromine are found in sea water and mineral springs.

Compounds of bromine and one other element are called bromides.

Bromine compounds are used to make rat poisons and products that treat wood for termite infestations.

 Iodine

Iodine is a purple-black solid. It is used in medicine, photography and dyes, and is produced in large quantities from sodium iodate.

Traces of iodine are found in foods, and without it our cells would not be able to convert food into energy. Large quantities of iodine are harmful.

 

Astatine

Astatine is an unstable, radioactive element. It is the heaviest of all halogens, but hardly any of it is found in nature.

Scientists estimate that only about 30g of astatine exists in the earth’s crust.

Scientists have been able to create more than 20 different astatine isotopes, through experiments.

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