Exist as diatomic molecules (pairs of atoms joined by covalent bonds)
Halogens
Fluorine
Chlorine
Bromine
Iodine
Fluorine
Very reactive, poisonous yellow gas
Chlorine
Fairly reactive, poisonous dense green gas
Bromine
Dense, poisonous, red-brown volatile liquid
Iodine
Dark grey crystalline solid or a purple vapour
As you go down Group 7
The halogens become less reactive, have higher melting and boiling points, and have higher relative atomic masses
All the Group 7 elements react in similar ways because they all have seven electrons in their outer shell
Halogens can form molecular compounds
Halogen atoms can share electrons via covalent bonding with other non-metals to achieve a full outer shell, e.g. HCl, PCl3, HF, CCl4
Halogens form ionic bonds with metals
They form 1- ions called halides (F-, Cl-, Br-, I-) when bonding with metals, forming ionic compounds like NaCl and FeBr3
Displacement reactions between halogens
1. A more reactive halogen will displace a less reactive halogen from solutions of its salts
2. e.g. Cl2 can displace Br- and I- from solutions, Br2 can displace I-
Fluorine, the most reactive halogen, will displace all the others, but it reacts so violently with water that you cannot carry out reactions in aqueous solutions
