Element 9 · Halogen
Fluorine (F) — Element 9
Latin fluere — to flow
Fluorine (F) is a halogen in Period 2, Group 17 of the periodic table with atomic number 9, standard atomic weight 18.998 u, and ground-state electron configuration [He] 2s² 2p⁵. At standard temperature and pressure it is classified as a gas with 7 valence electrons and common oxidation states -1.
Toothpaste, Teflon, uranium enrichment
What are the atomic properties and physical constants of Fluorine?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 9
- Standard atomic mass
- 18.998 u
- Chemical family
- Halogen
- Ground-state configuration
- [He] 2s² 2p⁵
- Electrons per shell
- 2, 7
- Valence electrons
- 7
- Common ion charges / oxidation states
- -1
- Phase at STP
- Gas
- Pauling electronegativity
- 3.98 Pauling
- First ionization energy
- 1,681 kJ/mol
- Atomic radius
- 42 pm
- Melting point
- -220 °C
- Boiling point
- -188 °C
- Discovery year
- 1886
- Table coordinate
- Period 2, Group 17
- Radioactivity
- Has stable isotope(s)
How are electrons arranged across Fluorine’s shells?
A neutral Fluorine atom contains 9 electrons distributed across 2 occupied principal energy shells ([He] 2s² 2p⁵). The table below compares Fluorine’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in F | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 2 e⁻ | 2 e⁻ |
| n = 2 | L | 7 e⁻ | 8 e⁻ |
Frequently Asked Questions about Fluorine (F)
What is the atomic mass and atomic number of Fluorine (F)?
Fluorine (F) has atomic number Z = 9 (9 protons in its nucleus) and an IUPAC standard atomic weight of 18.998 u. It sits in Period 2, Group 17 and is classified as a halogen.
What is the ground-state electron configuration of Fluorine?
The neutral ground-state electron configuration of Fluorine (Z = 9) is [He] 2s² 2p⁵. Across its 2 occupied principal shells (n = 1 to n = 2), the electrons per shell are 2, 7, with 7 valence electrons participating in bonding.
What are the common ion charges and electronegativity of Fluorine?
Fluorine commonly forms -1 oxidation states or ion charges in compounds. Its Pauling electronegativity is 3.98 and its first ionization energy is 1,681 kJ/mol.
When was Fluorine discovered and what is it used for?
Fluorine was discovered in 1886 (Latin fluere — to flow). Toothpaste, Teflon, uranium enrichment
How does Fluorine compare to neighboring elements?
Other halogen elements: