Fluorine
Pronunciation | /ˈ f l ʊər iː n, -ɪ n, -aɪ n/ (FLOOR-een, -⁠in, -⁠yn) /ˈ f l ɔːr iː n, -ɪ n, -aɪ n/ (FLOR-een, -⁠in, -⁠yn)
Allotropes | alpha, beta
Appearance | gas: very pale yellow liquid: bright yellow solid: alpha is opaque, beta is transparent
Standard atomic weight Ar, std(F) | 18.998403 163(6)
Atomic number (Z) | 9
Group | group 17 (halogens)
Period | period 2
Block | p-block
Element category | Reactive nonmetal
Electron configuration | [He] 2s2 2p5
Electrons per shell | 2, 7
Phase at STP | gas
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 point | 53.48 K, ​90 kPa
Critical point | 144.41 K, 5.1724 MPa
Heat of vaporization | 6.51 kJ/mol
Molar heat capacity | Cp: 31 J/(mol·K) (at 21.1 °C) Cv: 23 J/(mol·K) (at 21.1 °C)
Oxidation states | −1 (oxidizes oxygen)
Electronegativity | Pauling scale: 3.98
Ionization energies | 1st: 1681 kJ/mol 2nd: 3374 kJ/mol 3rd: 6147 kJ/mol (more)
Covalent radius | 64 pm
Van der Waals radius | 135 pm
Natural occurrence | primordial
Thermal conductivity | 0.02591 W/(m·K)
Magnetic ordering | diamagnetic (−1.2×10−4)
CAS Number | 7782-41-4
Naming | after the mineral fluorite, itself named after Latin fluo (to flow, in smelting)
Discovery | André-Marie Ampère (1810)
First isolation | Henri Moissan (June 26, 1886)
Named by | Humphry Davy