Fluorine (F)
Fluorine is the 9th element, a halogen in the p-block. Its standard atomic weight is 18.998.
Fluorine
18.998
What the table records
- Atomic number
- 9
- Standard atomic weight
- 18.998
- Group
- 17
- Period
- 2
- Block
- p-block
- Category
- Halogen
- [He] 2s2 2p5
- Valence electrons
- 7
- Typical valence
- 1
- Van der Waals radius
- 1.5 Å
- Covalent radius
- 0.57 Å
Molecules containing fluorine
The lightest named structures in this library that contain F.
Atomic fluorine
F · 19 g/mol
Fluoride Ion
F- · 19 g/mol
Hydrofluoric Acid
HF · 20.01 g/mol
Boron difluoride
BF₂ · 48.81 g/mol
Acetonitrile, fluoro-
C₂H₂FN · 59.04 g/mol
3-Fluoropropene
C₃H₅F · 60.07 g/mol
Fluoro(dioxido)borane
BFO₂-2 · 61.81 g/mol
2-Fluoroethylamine
C₂H₆FN · 63.08 g/mol
2-Fluoroethanol
C₂H₅FO · 64.06 g/mol
2-Fluoroethylazanium
C₂H₇FN+ · 64.08 g/mol
Carbonyl fluoride
CF₂O · 66.01 g/mol
Boron trifluoride
BF₃ · 67.81 g/mol
How to read these numbers
The standard atomic weight is an average over the isotopes as they occur naturally, which is why it is rarely a whole number. It is the figure a molar mass calculation uses. Work in mass spectrometry wants the monoisotopic mass of a single isotope instead, which is a different number.
The two radii are not the same measurement. The covalent radius is half the distance between two bonded atoms of the element; the van der Waals radius is how close a non-bonded atom gets before repulsion takes over, and is always the larger. Space-filling models are drawn with the second, ball-and-stick models with the first — which is why the same molecule looks so different in the two.