Fluorine
Pronunciation
  • /ˈflʊərn, -ɪn, -n/
    (FLOOR-een, -⁠in, -⁠yn)
  • /ˈflɔːrn, -ɪn, -n/
    (FLOR-een, -⁠in, -⁠yn)
Allotropesalpha, beta
Appearancegas: very pale yellow
liquid: bright yellow
solid: alpha is opaque, beta is transparent
Standard atomic weight Ar, std(F)18.998403163(6)
Atomic number (Z)9
Groupgroup 17 (halogens)
Periodperiod 2
Blockp-block
Element category  Reactive nonmetal
Electron configuration[He] 2s2 2p5
Electrons per shell
2, 7
Phase at STPgas
Melting point(F2) 53.48 K ​(−219.67 °C, ​−363.41 °F)
Boiling point(F2) 85.03 K ​(−188.11 °C, ​−306.60 °F)
Density (at STP)1.696 g/L
when liquid (at b.p.)1.505 g/cm3
Triple point53.48 K, ​90 kPa
Critical point144.41 K, 5.1724 MPa
Heat of vaporization6.51 kJ/mol
Molar heat capacityCp: 31 J/(mol·K) (at 21.1 °C)
Cv: 23 J/(mol·K) (at 21.1 °C)
Oxidation states−1 (oxidizes oxygen)
ElectronegativityPauling scale: 3.98
Ionization energies
  • 1st: 1681 kJ/mol
  • 2nd: 3374 kJ/mol
  • 3rd: 6147 kJ/mol
  • (more)
Covalent radius64 pm
Van der Waals radius135 pm
Natural occurrenceprimordial
Thermal conductivity0.02591 W/(m·K)
Magnetic orderingdiamagnetic (−1.2×10−4)
CAS Number7782-41-4
Namingafter the mineral fluorite, itself named after Latin fluo (to flow, in smelting)
DiscoveryAndré-Marie Ampère (1810)
First isolationHenri Moissan (June 26, 1886)
Named byHumphry Davy