Chlorine 17 Cl 35.453(2)   Switch element to... actinium aluminium aluminum americium antimony argon arsenic astatine barium berkelium beryllium bismuth bohrium boron bromine cadmium caesium calcium californium carbon cerium cesium chlorine chromium cobalt copper curium darmstadtium dubnium dysprosium einsteinium erbium europium fermium fluorine francium gadolinium gallium germanium gold hafnium hassium helium holmium hydrogen indium iodine iridium iron krypton lanthanum lawrencium lead lithium lutetium magnesium manganese meitnerium mendelevium mercury molybdenum neodymium neon neptunium nickel niobium nitrogen nobelium osmium oxygen palladium phosphorus platinum plutonium polonium potassium praseodymium promethium protactinium radium radon rhenium rhodium roentgenium rubidium ruthenium rutherfordium samarium scandium seaborgium selenium silicon silver sodium strontium sulfur sulphur tantalum technetium tellurium terbium thallium thorium thulium tin titanium tungsten ununbium ununhexium ununoctium ununpentium ununquadium ununtrium uranium vanadium xenon ytterbium yttrium zinc zirconium Go adjacent... O F Ne S Cl Ar Se Br Kr

The essentials

Description 

Here is a brief description of chlorine.

• Standard state: gas at 298 K
• Colour: yellowish green
• Classification: Non-metallic
• Availability:

Image adapted with permission from Prof James Marshall's (U. North Texas, USA) Walking Tour of the elements CD.

Chlorine is a greenish yellow gas which combines directly with nearly all elements. Chlorine is a respiratory irritant. The gas irritates the mucous membranes and the liquid burns the skin. As little as 3.5 ppm can be detected as an odour, and 1000 ppm is likely to be fatal after a few deep breaths. It was used as a war gas in 1915. It is not found in a free state in nature, but is found commonly as NaCl (solid or seawater).

Nearing Zero cartoon included by kind permission of Nick Kim.

Isolation

It is rarely necessary to make chlorine in the laboratory as it is readily available commercially in cylindes. Chlorine is found largely in seawater where it exists as sodium chloride. It is recovered as a reactive, corrosive, pale green chlorine gas from brine (a solution of sodium chloride in water) by electrolyis. Electrolysis of molten salt, NaCl, also succeeds, in which case the other product is sodium metal rather than sodium hydroxide.

Na⁺ + Cl^- + H₂O → Na⁺ + ¹/₂Cl₂ + ¹/₂H₂ + OH^-

In the laboratory under carefully controlled conditions, chlorine can be made by the action of an oxidizing agent such as manganese dioxide, MnO₂, upon concentrated hydrochloric acid - the same reaction used by Scheele in 1774 when discovering chlorine.

MnO₂ + 4HCl → MnCl₂ + Cl₂ + 2H₂O

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