Chemical Element: chlorine

(Greek: chloros, grass-green; a reference to the color of the gas which tends to be greenish-yellow; gas)

Chemical-Element Information

Symbol: Cl
Atomic number: 17
Year discovered: 1774 or 1810

Discovered by: Karl Wilhelm Scheele (1742-1786), a Swedish chemist, and credit is given to Sir Humphry Davy for showing that chlorine was an element not an oxygen compound.


  • Karl Wilhelm Scheele discovered many simple compounds from plants and animals, to say nothing of such poisonous gases as hydrogen fluoride, hydrogen sulfide, and hydrogen cyanide.
  • Scheele was also involved in the discovery of a number of elements, though he never managed to get undisputed credit for a single one of them.
  • By 1774, he had done most of the preliminary work that led to the discovery of the element manganese.
  • His friend, the Swedish mineralogist Johan Gottlieb Gahn (1745-1818); however, completed the final step and got credit for the discovery.
  • Again, in 1774, Scheele isolated the gas chlorine, which was unusual in that it was not colorless.
  • Chlorine is greenish-yellow and its name is derived from the Greek word for “green”.
  • Scheele’s problem was that he didn’t recognize chlorine to be an element because he thought it was a combination of some substance with oxygen.
  • Since Scheele thought the resulting gas contained oxygen, Sir Humphry Davy proposed and confirmed chlorine to be an element in 1810, and he also named the element.
  • Scheele obtained chlorine through the reaction of the mineral pyrolusite (manganese dioxide) with hydrochloric acid (then known as muriatic acid).
  • Davy had worked with hydrochloric acid (a strong acid) and he showed that it contained no oxygen.
  • This was the final blow to the general assumption that oxygen was essential to acids.
  • Hydrochloric acid did contain chlorine, and Scheele thought chlorine was an oxygen-containing compound.
  • In 1810, Davy showed this was not true, and that chlorine was an element.
  • For this reason, Davy, rather than Scheele usually receives credit for the discovery of chlorine.

Name in other languages:

French: chlore

German: Chlor

Italian: cloro

Spanish: cloro


Information about other elements may be seen at this Chemical Elements List.

A special unit about words that include chemo-, chem- may be seen here.