Chlorine

The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. It is the second-most abundant halogen (after fluorine) and twenty-first most abundant chemical element in Earth's crust. Chlorine is the second halogen, being a nonmetal in group 17 of the periodic table.

The halogens are a group in the periodic table consisting of five chemically related elements: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At).

The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Its properties are thus similar to fluorine, bromine, and iodine, and are largely intermediate between those of the first two.

Its properties are thus intermediate between those of chlorine and iodine.

Because of its great reactivity, all chlorine in the Earth's crust is in the form of ionic chloride compounds, which includes table salt.

It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents.

The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Its properties are thus similar to fluorine, bromine, and iodine, and are largely intermediate between those of the first two.

It also has a high electron affinity, second only to chlorine, and tends to capture an electron to become isoelectronic with the noble gas neon; it has the highest electronegativity of any element.

The high oxidising potential of elemental chlorine led to the development of commercial bleaches and disinfectants, and a reagent for many processes in the chemical industry.

In wastewater treatment, a disinfection step with chlorine, ultra-violet (UV) radiation or ozonation can be included as tertiary treatment to remove pathogens from wastewater, for example if it is to be reused to irrigate golf courses.

Carl Wilhelm Scheele wrote a description of chlorine gas in 1774, supposing it to be an oxide of a new element.

For example, Scheele discovered oxygen (although Joseph Priestley published his findings first), and identified molybdenum, tungsten, barium, hydrogen, and chlorine before Humphry Davy, among others.

The most common compound of chlorine, sodium chloride (common salt), has been known since ancient times.

It is the starting point for the chloralkali process, the industrial process to produce chlorine and sodium hydroxide, according to the chemical equation

In the upper atmosphere, chlorine-containing organic molecules such as chlorofluorocarbons have been implicated in ozone depletion.

Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated paraffin hydrocarbons that contain only carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivative of methane, ethane, and propane.

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

Modern bleaches resulted from further work by Berthollet, who first produced sodium hypochlorite in 1789 in his laboratory in the town of Javel (now part of Paris, France), by passing chlorine gas through a solution of sodium carbonate.

The compound in solution is unstable and easily decomposes, liberating chlorine, which is the active principle of such products.

The effect on the allies was devastating because the existing gas masks were difficult to deploy and had not been broadly distributed.

Airborne toxic materials may be gaseous (for example, mustard gas and chlorine gas) or particulates (such as biological agents).

Elemental chlorine at high concentrations is extremely dangerous and poisonous for all living organisms, and was used in World War I as the first gaseous chemical warfare agent.

These included chlorine and phosgene gas.

Chlorine is used in the manufacture of a wide range of consumer products, about two-thirds of them organic chemicals such as polyvinyl chloride, and many intermediates for the production of plastics and other end products which do not contain the element.

About 57% of the mass of PVC is chlorine.

In the upper atmosphere, chlorine-containing organic molecules such as chlorofluorocarbons have been implicated in ozone depletion.

Ozone can be destroyed by a number of free radical catalysts; the most important are the hydroxyl radical (OH·), nitric oxide radical (NO·), chlorine radical (Cl·) and bromine radical (Br·).

Scheele observed several of the properties of chlorine: the bleaching effect on litmus, the deadly effect on insects, the yellow-green color, and the smell similar to aqua regia.

These reactions result in the volatile products nitrosyl chloride and Chlorine gas as evidenced by the fuming nature and characteristic yellow color of aqua regia.

Elemental chlorine at high concentrations is extremely dangerous and poisonous for all living organisms, and was used in World War I as the first gaseous chemical warfare agent.

On 22 April 1915, at the Second Battle of Ypres, the Germans (violating the Hague Convention) used chlorine gas for the first time on the Western Front.

Scottish chemist and industrialist Charles Tennant first produced a solution of calcium hypochlorite ("chlorinated lime"), then solid calcium hypochlorite (bleaching powder).

This compound is relatively stable and has greater available chlorine than sodium hypochlorite (liquid bleach).

It is the second-most abundant halogen (after fluorine) and twenty-first most abundant chemical element in Earth's crust.

Its properties are thus similar to fluorine, bromine, and iodine, and are largely intermediate between those of the first two.

Ampère had given some of his sample to English chemist Humphry Davy (1778–1829), who experimented on the substance and noted its similarity to chlorine.

It is an extremely reactive element and a strong oxidising agent: among the elements, it has the highest electron affinity and the third-highest electronegativity on the Pauling scale, behind only oxygen and fluorine.

It is an extremely reactive element and a strong oxidising agent: among the elements, it has the highest electron affinity and the third-highest electronegativity on the Pauling scale, behind only oxygen and fluorine.

Chlorine most strongly attracts extra electrons; neon most weakly attracts an extra electron.

Chlorine is the second halogen, being a nonmetal in group 17 of the periodic table.

The elements generally classified as nonmetals include one element in group 1 (hydrogen); one in group 14 (carbon); two in group 15 (nitrogen and phosphorus); three in group 16 (oxygen, sulfur and selenium); most of group 17 (fluorine, chlorine, bromine and iodine); and all of group 18 (with the possible exception of oganesson).

He called it "dephlogisticated muriatic acid air" since it is a gas (then called "airs") and it came from hydrochloric acid (then known as "muriatic acid").

Joseph Priestley of Leeds, England prepared pure hydrogen chloride in 1772, and by 1808 Humphry Davy of Penzance, England had proved that the chemical composition included hydrogen and chlorine.

36 Cl occurs in trace quantities in nature as a cosmogenic nuclide in a ratio of about (7–10) × 10 −13 to 1 with stable chlorine isotopes: it is produced in the atmosphere by spallation of 36 Ar by interactions with cosmic ray protons.

Chlorine has two stable isotopes and one naturally occurring radioactive isotope, the cosmogenic isotope 36 Cl.

Common chemical theory at that time held that an acid is a compound that contains oxygen (remnants of this survive in the German and Dutch names of oxygen: sauerstoff or zuurstof, both translating into English as acid substance), so a number of chemists, including Claude Berthollet, suggested that Scheele's dephlogisticated muriatic acid air must be a combination of oxygen and the yet undiscovered element, muriaticum.

He also carried out research into dyes and bleaches, being first to introduce the use of chlorine gas as a commercial bleach in 1785.