Our Elements
Menu

Chlorine

Element 17 · Halogen

Specimen

Atomic number
17
Atomic mass
35.45
State at room temperature
Gas
Melting point
-101.5 °C
Boiling point
-34.04 °C
Density
0.003214 g/cm³
Discovered
1774

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

Can I eat it?

In food and water
Your body needs it. As chloride, mostly from table salt, chlorine is a nutrient. The US and Canadian intakes for chloride match those for sodium. The EU lists chloride as a mineral that food makers can add to foods. 34

See every element.

The atom

Cl
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) outermost 7
Total17

Configuration [Ne] 3s² 3p⁵

3s ↑ ↓
3p ↑ ↓ ↑ ↓ ↑
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 17 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 Ne core, with one arrow per electron.

Related elements

Group 17
F Fluorine Br Bromine I Iodine At Astatine Ts Tennessine

New elements by e-mail

Sources

  1. 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. 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. 3

    Health Canada, from the Institute of Medicine (US) Dietary Reference Intakes reports, 2010. Dietary Reference Intakes tables (Institute of Medicine values), updated November 2010 , Reference Values for Elements, footnotes 20 to 27.

    The joint US and Canadian reference intakes. The values are from the Institute of Medicine reports of 1997 to 2004 and 2010.

    • Sodium and chloride are normally found in foods together as sodium chloride (table salt). For this reason, the AI and UL for chloride are set at a level equivalent on a molar basis to those for sodium
  4. 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 ... Fluoride Chloride Phosphorus
  5. 5

    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.