Fluorine (F)
Fluorine is element 9, a halogen in period 2, group 17 of the periodic table. At room temperature it is a gas.
Electron configuration [He] 2s2 2p5
Electrons per shell 2, 7
Fluorine data
| Atomic number | 9 |
|---|---|
| Symbol | F |
| Atomic mass | 18.998 u |
| Category | Halogen |
| Group | 17 |
| Period | 2 |
| Block | p |
| State at 25 °C | gas |
| Melting point | 54 K (-219.1 °C) |
| Boiling point | 85 K (-188.1 °C) |
| Density | 0.001696 g/cm³ (1.696 g/L) |
| Electronegativity (Pauling) | 3.98 |
| Atomic radius | 71 pm |
| 1st ionization energy | 1681 kJ/mol |
| Electron affinity | -328 kJ/mol |
| Oxidation states | -1 |
| Common ion charge | − |
| Discovered | 1670 |
Orbital diagram
Each box is one orbital holding up to two electrons of opposite spin. Following Hund’s rule, electrons spread out singly across a subshell before pairing.
Work through fluorine’s configuration and its ions →
Where fluorine sits
Fluorine belongs to the halogens. Its Pauling electronegativity of 3.98 puts it among the strongest electron-pullers on the table; see the electronegativity chart and periodic trends for context. To use its mass in a calculation, try the molar mass calculator.
Fluorine FAQ
What is the electron configuration of fluorine?
Fluorine (Z = 9) has the configuration 1s2 2s2 2p5. In noble-gas shorthand that is [He] 2s2 2p5.
How many valence electrons does fluorine have?
7 (outer shell (n = 2)).
What is the atomic mass of fluorine?
The standard atomic weight of fluorine is 18.998 u, so one mole weighs 18.998 g.
Is fluorine a metal?
No. Fluorine is a halogen.
What is the charge of a fluorine ion?
Fluorine most commonly forms F−.