Group 7: The Halogens
Halogens are group seven elements. Their elements are diatomic molecules. They exist in pairs, such as F2 and Cl2. These two elements are gases, bromine is a liquid and iodine is a solid. Astatine is radioactive.
These vapours and gases are poisonous. All these elements need to be handled in a fume cupboard.
| Element | State | Colours |
| Flourine | Gas | Yellow |
| Chlorine | Gas | Green |
| Bromine | Liquid | Orange – Brown vapour |
| Iodine | Solid | Dark Grey – Purple vapour |
| Halogen | Reaction with Hydrogen |
| Flourine | Violent explosion, even in the cold and dark |
| Chlorine | Violent explosion if exposed to a flame or sunlight |
| Bromine | Mild explosion if a bromine vapour/hydrogen mixture is exposed to a flame |
| Iodine | Partial reaction to from hydrogen iodide if vapour is heated continuously with hydrogen |
Reactions with Hydrogen
The halogens react with hydrogen to form hydrogen halides such as hydrogen fluoride and hydrogen chloride. These are all steamy, acidic and poisonous gases. They are very soluble in water, reacting with it to produce solutions of acids. However as a gas, it is NOT an acid.