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Chlorine

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Chlorine is a chemical element with symbol Cl and atomic number 17. It also has a relative atomic mass of 35.5. Chlorine is in the halogen group (17) and is the second lightest halogen following fluorine.

The element is a yellow-green gas under standard conditions, where it forms diatomic molecules. Chlorine has the highest electron affinity and the third highest electronegativity of all the reactive elements. For this reason, chlorine is a strong oxidizing agent. Free chlorine is rare on Earth, and is usually a result of direct or indirect oxidation by oxygen.

The most common compound of chlorine, sodium chloride (common salt), has been known since ancient times. Around 1630, chlorine gas was first synthesized in a chemical reaction, but not recognized as a fundamentally important substance. Characterization of chlorine gas was made in 1774 by Carl Wilhelm Scheele, who supposed it to be an oxide of a new element. In 1809, chemists suggested that the gas might be a pure element, and this was confirmed by Sir Humphry Davy in 1810, who named it from Ancient Greek: χλωρóς (khlôros) "pale green".

Nearly all chlorine in the Earth's crust occurs as chloride in various ionic compounds, including table salt. It is the second most abundant halogen and 21st most abundant chemical element in Earth's crust. Elemental chlorine is commercially produced from brine by electrolysis. The high oxidizing potential of elemental chlorine led commercially to free chlorine's bleaching and disinfectant uses, as well as its many uses of an essential reagent in the chemical industry. Chlorine is used in the manufacture of a wide range of consumer products, about two-thirds of them organic chemicals such as polyvinyl chloride, as well as many intermediates for production of plastics and other end products which do not contain the element. As a common disinfectant, elemental chlorine and chlorine-generating compounds are used more directly in swimming pools to keep them clean and sanitary.

In the form of chloride ions, chlorine is necessary to all known species of life. Other types of chlorine compounds are rare in living organisms, and artificially produced chlorinated organics range from inert to toxic. In the upper atmosphere, chlorine-containing organic molecules such as chlorofluorocarbons have been implicated in ozone depletion.

Chlorine. Chlorine is a chemical element with symbol Cl and atomic number 17.

Chlorine

It also has a relative atomic mass of 35.5. Chlorine is in the halogen group (17) and is the second lightest halogen following fluorine. The element is a yellow-green gas under standard conditions, where it forms diatomic molecules.

Characteristics

History. Production. Applications. Health effects and hazards. Organochlorine compounds as pollutants. Reductive dechlorination. Reductive dechlorination is degradation of chlorinated organic compounds by chemical reduction with release of inorganic chloride ions.

Reductive dechlorination

Biological[edit] In a biological context chlorine behaves similarly to other atoms in the halogen chemical series, and thus reductive dechlorination can be considered to fall within a somewhat broader class of biological reactions known as reductive dehalogenation reactions, in which the removal of a halogen substituent from an organic molecule occurs with a simultaneous addition of electrons to the molecule.

This can be further subdivided into two types of reaction processes, the first of which, hydrogenolysis, is the replacement of the halogen atom with a hydrogen atom. The second, vicinal reduction (sometimes called, dihaloelimination), involves the removal of two halogen atoms that are adjacent on the same alkane or alkene molecule, leading to the formation of an additional carbon-carbon bond.[1] Electrochemical[edit] Radiation[edit] References[edit] Polymer degradation. Polymer degradation is a change in the properties—tensile strength, colour, shape, etc.

Polymer degradation

—of a polymer or polymer-based product under the influence of one or more environmental factors such as heat, light or chemicals such as acids, alkalis and some salts. These changes are usually undesirable, such as cracking and chemical disintegration of products or, more rarely, desirable, as in biodegradation, or deliberately lowering the molecular weight of a polymer for recycling.

The changes in properties are often termed "aging". In a finished product such a change is to be prevented or delayed. Degradation can be useful for recycling/reusing the polymer waste to prevent or reduce environmental pollution. Polymeric molecules are very large (on the molecular scale), and their unique and useful properties are mainly a result of their size.

Commodity polymers[edit] Close-up of broken fuel pipe from road traffic accident. Industrial gas. A gas regulator attached to a nitrogen cylinder.

Industrial gas

Chloride. The chloride ion /ˈklɔraɪd/[3] is the anion (negatively charged ion) Cl−.

Chloride

Chloramine. Chloramines are derivatives of ammonia by substitution of one, two or three hydrogen atoms with chlorine atoms: monochloramine (chloroamine, NH2Cl), dichloramine (NHCl2), and nitrogen trichloride (NCl3).[1] The term chloramine also refers to a family of organic compounds with the formulas R2NCl and RNCl2 (R is an organic group).

Chloramine

Monochloramine (chloroamine) is an inorganic compound with the formula NH2Cl.