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Halogens

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Submitted By ocymoronli
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1) General
Halogens are a group of nonmetal elements from group 7 of the Periodic Table. It contains fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and astatine (At). Ununseptium (Uus) is an artificially created element and it is sometimes considered to be a halogen. Halogens have a valency of 1 and a halogen ion has a charge of 1-.

Like other groups, there are similarities and trends (both physical and chemical) within the different elements in this group. Below is a table showing the electronic configuration and formula of the halogens.
|Halogen |Room temperature (20 oC) |Vapour Colour |
|Fluorine |Yellow Gas |Yellow |
|Chlorine |Green Gas |Green |
|Bromine |Red/Brown Liquid |Orange |
|Iodine |Dark Grey/Violet Solid |Purple/Violet |
|Astatine |Black Solid |Dark Purple |

The halogens become darker as you go down the group. Fluorine is very pale yellow, chlorine is yellow-green and bromine is red-brown. Iodine crystals are shiny purple-black but easily turn into a dark purple vapour when they are warmed up.

Common properties
The halogens have the following properties in common: • they are non-metals • they have low melting and boiling points • they are brittle when solid • they are poor conductors of heat and electricity • they have coloured vapours • their molecules each contain two atoms (they are diatomic)

Similarities

|Halogen |Atomic Number |Electronic Configuration |Formula |
|Fluorine |9 |2, 7

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