Page 6 - Curriculum Visions Dynamic Book

The halogens
The halogens – fluorine, chlorine, bromine and iodine – occur in the same group of
the periodic table and therefore have many characteristics in common. Some of these are shown on these two pages.
 (left) Chlorine gas; (middle) bromine vapour over bromine liquid, (right) iodine vapour over solid crystals of iodine (iodine does not occur as a liquid). Note: Fluorine is so dangerous, it is never used in school and college demonstrations and so is not shown here.
Also... Why halogens are so reactive
Each of the elements in the halogen family contains seven electrons in its outermost electron shell. To be stable it needs to have eight. As a result the atoms react with other elements to gain an electron and fill the shell.
The smallest atoms try to fill their electron shell most vigorously, and as fluorine is the smallest of the family,
it is the most reactive. Iodine has the largest atoms and is the least reactive of the family (see pages 44 and 45).
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