Fluorine is the 9th element of the periodic table and it has a atomic weight of 18.998403163. It is a halogen, which makes it very reactive with all elements except for Helium and Neon. It is in fact the most reactive not metal and more reactive that any metal except Caesium, which is on par with it. Fluorine has little uses as it is so reactive and none in its pure form, but as fluoride is is used in toothpaste. 

Name: Fluorine                                                      Melting point: -219.67 C, -363.41 F

Atomic number: 9                                                  Boiling point: -188.11 C, -306.60 F

Atomic weight: 18.998403163

Elemental category: Halogen

Colour: Pale yellow as a gas, bright yellow as a liquid or solid.

Previous element: Oxygen  Next element: Neon

Link to a video of fluorine experiments: