Chemical element · Atomic number 9
Fluorine
Fluorine in the periodic table: atomic number 9, electron configuration, atomic mass, physical data, oxidation states, media credit and visible sources.
Halogen
gaseous
18.99840316 u
Documented element sampleLiquid fluorine at about minus 196 degrees Celsius; photographs like this are rare because the element is so reactive.
Image credit: Prof. Dr. Sebastian Riedel (Freie Universität Berlin)
Auto-oriented, limited to 1600 × 1200 pixels and re-encoded as WebP; the subject was not altered.
Atomic classification
Shell occupancy
Fluorine in the Bohr shell model
This shows the electron distribution of the neutral atom in a simplified shell model.
- K · n=1
- 2 electrons
- L · n=2
- 7 electrons
- Electron configuration
- [He]2s2 2p5
- Electrons per shell
- 2 · 7
- Group
- 17
- Period
- 2
- Block
- P
- Element category
- Halogen
Physical and chemical properties
- Atomic mass
- 18.99840316 u
- Standard state
- gaseous
- Density
- 0.001696 g/cm³
- Melting point
- 53.53 K
- Boiling point
- 85.03 K
- Electronegativity
- 3.98 (Pauling)
- First ionisation energy
- 17.423 eV
- Oxidation states
- -1
- Discovery
- 1670
Safety and periodic classification
Safety
Safe handling cannot be inferred from Fluorine's position in the periodic table alone. Laboratory, classroom and disposal decisions must follow the documentation for the exact material and its safety data sheet.
Position and comparison
Fluorine is in period 2, group 17 and the P block. Its direct neighbours by atomic number are Oxygen and Neon. The recorded Pauling electronegativity is 3.98. Periodic trends are compared only through the separately sourced neighbouring values.
Sources and scope
PubChem attributes element data to sources including IUPAC, NIST and IAEA. Quanta stores the referenced snapshot locally and leaves unknown values unavailable.
Where Fluorine sits among the 118 elements
The table compares the reported values for Fluorine with every other element that carries the same value in the snapshot. A rank is not a judgement, it is orientation: it says how unusual this value is across the periodic table.
| Value | Fluorine | Position in the data set |
|---|---|---|
| Melting point | 53.53 K | Rank 100 of 103 elements with a reported value. Highest: Carbon. |
| Boiling point | 85.03 K | Rank 89 of 93 elements with a reported value. Highest: Rhenium. |
| Density | 0.002 g/cm³ | Rank 91 of 96 elements with a reported value. Highest: Osmium. |
| Electronegativity (Pauling) | 3.98 | Rank 1 of 95 elements with a reported value. Highest: Fluorine. |
| Ionisation energy | 17.423 eV | Rank 3 of 102 elements with a reported value. Highest: Helium. |
All values and ranks come from the PubChem Periodic Table snapshot, retrieved on 2026-07-15. Elements without a reported value are excluded, so the population differs per row.
The neighbours of Fluorine in the periodic table
- Place in the table
- Group 17, period 2, P block. Classified as halogen, gaseous at standard conditions.
- Direct neighbours
- Atomic number 9. Preceded by Oxygen, followed by Neon.
- Same group
- Same number of outer electrons, and therefore similar reactivity to Chlorine, Bromine, Iodine, Astatine, Tennessine.
- Discovery
- Recorded in the snapshot as: 1670. Who, where and under what circumstances is not part of that record, so this page carries the sourced year and no discovery narrative.
- Oxidation states
- -1. They follow from the electron configuration [He]2s2 2p5 and indicate which compounds to expect.
Go from looking up chemistry to remembering it.
Turn your notes into source-backed study cards and review them at the right time.
Starter stays free · no payment details