Page 4 - Curriculum Visions Dynamic Book

An element is a substance that cannot be broken down into a simpler substance by any known means. Each of the 92 naturally occurring elements is therefore one of the fundamental materials from which everything in the Universe is made.
The halogens
The elements that together we call the halogens can all be found in the sea. The ancient Greeks knew where to find them because the word “halogen” comes from the Greek word meaning “salt- producing”. Although you cannot see
any trace of salt, taste sea water and you will find that it is salty, for dissolved in the water
is sodium chloride, a compound
of chlorine, one of the halogens,
and sodium. Sodium chloride is commonly known as table salt.
Sodium chloride is not the only salt in sea water. You will also find salts containing fluorine (as in the fluoride put into your toothpaste), iodine (as in the substance used to iodise table salt) and bromine (as in the bromide used on photographic film).
The sea contains natural collectors of some of these valuable elements. In particular, iodine is gathered by seaweed and stored in its tissues.
Each of the halogen elements is so reactive you will never find a halogen alone. Halogens bind so
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