The most reactive element on the Periodic Table, fluorine has a violent history in the quest for its discovery. Despite the difficult and sometimes explosive properties of fluorine, it is a vital element for humans and animals, which is why it is commonly found in drinking water and toothpaste.
Just the facts
Atomic number (number of protons in the nucleus): 9
Atomic symbol (on the Periodic Table of Elements): F
Atomic weight (average mass of the atom): 18.998
Density: 0.001696 grams per cubic centimeter
Phase at room temperature: Gas
Melting point: minus 363.32 degrees Fahrenheit (minus 219.62 degrees Celsius)
Boiling point: minus 306.62 degrees F (minus 188.12 degrees C)
Number of isotopes (atoms of the same element with a different number of neutrons): 18
Most common isotopes: F-19 (100 percent natural abundance)
History
Early chemists tried for years to isolate the element from various fluorides. It wasn't until 1986 that German chemist Karl O. Christie successfully synthesized fluorine, and reported his results in the journal Inorganic Chemistry. Fluorine does not occur free in nature; but in 2012, researchers found small amounts of fluorine trapped in antozonite, a type of radioactive fluorite.
For centuries, the mineral fluorspar was used in metal refining. Known today as calcium fluoride (CaF2), it was used as a flux to separate pure metal from the unwanted minerals in ore, according to Chemicool. The "fluor" comes from the Latin word "fluere," meaning "to flow," because that's what fluorspar allowed metals to do. The mineral was also called Bohemian emerald and was used in glass etching, according to the Jefferson Laboratory.