Fluorine

Symbol: F
Atomic number: 9
Category: halogens
Group: 17
Period: 2
Block: p
Atomic weight: 18.9984032 g/mol
Electrons per shell: 2, 7
CAS number: 7782-41-4
Phase: gas
Density: 1.7 g/l (0 C, 101.325 kPa)
Melting point: 53.53 K (-219.62 C, -363.32 F)
Boiling point: 85.03 K (-188.12 C, -306.62 F)
Crystal structure: cubic
Oxidation states: -1
Electronegativity: 3.98 (Pauling scale)
Name's origin: fluere
Name's meaning: a Latin word which means 'to flow' - fluorine was used as a flux which promotes the flow of molten metals
Facts:
- forms a single bond with itself in elemental form, resulting in the diatomic F2 molecule
- is a supremely reactive, poisonous, pale, yellowish-brown gas
- is the most chemically reactive and electro-negative of all the elements
- is highly dangerous because it readily burns hydrocarbons, more so than other halogens such as the poisonous chlorine gas
- though F2 is too reactive to have any natural biological role, fluorine is incorporated into compounds with biologic
- is not an essential nutrient, but its important in preventing tooth decay is well-recognized, and thus used in tooth pastes
- has a characteristic pungent odor that is detectable in concentrations as low as 20 ppb
- the lethal dose of sodium fluoride in rats is 52 mg/kg