Fluorine

Element 9 · Halogen

Specimen

Atomic number: 9
Atomic mass: 18.998
State at room temperature: Gas
Melting point: -219.6 °C
Boiling point: -188.1 °C
Density: 0.001696 g/cm³
Discovered: 1670

Atomic mass from IUPAC.¹ Other physical data from PubChem.²

Can I eat it?

In food and water: Allowed in food. As fluoride, it is in water, tea and sea fish. The EU lets food makers add fluoride to foods. EFSA says fluoride is not an essential nutrient. It still sets an adequate intake, because fluoride helps prevent tooth decay. High amounts can harm health. ³⁴⁵

The atom

Shell	Electrons
1 (K)	2
2 (L) outermost	7
Total	9

Configuration [He] 2s² 2p⁵

2s ↑ ↓

2p ↑ ↓ ↑ ↓ ↑

Fluorine-19
Protons	9
Neutrons	10
Mass number	19

A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 9 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the He core, with one arrow per electron.

Related elements

Sources

1

IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), 2024. Abridged Standard Atomic Weights 2024 .

The atomic mass shown for the 84 elements that have a standard atomic weight.
2

National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

Electron configuration, melting and boiling points, density and discovery year for all 118 elements.
3
European Food Safety Authority (EFSA), 2017. Dietary Reference Values for nutrients. Summary report (amended 2019) .

Summaries of the EFSA NDA Panel opinions on each vitamin and mineral, section 4 (minerals) and section 5 (cobalamin).
- Major dietary fluoride sources are water and water-based beverages or foods reconstituted with fluoridated water, tea, marine fish ... As fluoride is not an essential nutrient ... Because of the beneficial effect of dietary fluoride on the prevention of caries, the Panel considered that the setting of an Adequate Intake (AI) is appropriate
4
European Parliament and Council of the European Union, 2006. Regulation (EC) No 1925/2006 on the addition of vitamins and minerals and of certain other substances to foods , Annex I, point 2 (minerals).

The text as adopted by the EU, from legislation.gov.uk. EUR-Lex served the quote checker an empty page.
- VITAMINS AND MINERALS WHICH MAY BE ADDED TO FOODS ... Molybdenum Fluoride Chloride Phosphorus
5
Agency for Toxic Substances and Disease Registry (ATSDR), 2014. ToxFAQs for Fluorides, Hydrogen Fluoride, and Fluorine .
- Small amounts of fluoride help prevent tooth cavities, but high levels can harm your health
6

National Institute of Standards and Technology (NIST), 2026. Atomic Weights and Isotopic Compositions for All Elements .

Isotopic composition of each element; the most abundant isotope sets the neutron count in the nucleus view.

Specimen

Can I eat it?

The atom

Related elements

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Sources