|Name, Symbol, Number||Chlorine, Cl, 17|
|Group, Period, Block||17 (VIIA), 3 , p|
|Density, Hardness||3.214 kg/m3 (273 K), NA|
|Atomic weight||35.5 amu|
|Atomic radius (calc.)||100 (79) pm|
|Covalent radius||99 pm|
|van der Waals radius||175 pm|
|Electron configuration||[Ne]3s3s2 3p5|
|e-'s per energy level||2, 8,7|
|Oxidation states (Oxide)||±1,3,5,7 (strong acid)|
|State of matter||gas (nonmagnetic)|
|Melting point||171.6 K (150.7 °F)|
|Boiling point||239.11 K (29.27 °F)|
|Molar volume||17.39 ×1010-3 m3/mol|
|Heat of vaporization||10.2 kJ/mol|
|Heat of fusion||3.203 kJ/mol|
|Vapor pressure||1300 Pa|
|Speed of sound||no data|
|Electronegativity||3.16 (Pauling scale)|
|Specific heat capacity||480 J/(kg*K)|
|Electrical conductivity||no data|
|Thermal conductivity||0.0089 W/(m*K)|
|1st ionization potential||1251.2 kJ/mol|
|2nd ionization potential||2298 kJ/mol|
|3rd ionization potential||3822 kJ/mol|
|4th ionization potential||5158.6 kJ/mol|
|5th ionization potential||6542 kJ/mol|
|6th ionization potential||9362 kJ/mol|
|7th ionization potential||11018 kJ/mol|
|8th ionization potential||33604 kJ/mol|
|9th ionization potential||38600 kJ/mol|
|10th ionization potential||43961 kJ/mol|
|Most Stable Isotopes|
|SI units & STP are used except where noted.|
|Table of contents|
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The pure chemical element has the physical form of a diatomic green gas. The name chlorine is derived from chloros, meaning green, referring to the color of the gas.
This element is a member of the salt-forming halogen series and is extracted from chlorides through oxidation and more commonly, by electrolysis. Chlorine is a greenish-yellow gas that combines readily with nearly all other elements. At 10 °C one liter of water dissolves 3.10 liters of chlorine and at 30 °C only 1.77 liters.
Chlorine is an important chemical in water purification, in disinfectants in bleach and in mustard gas.
Chlorine is also used widely in the manufacture of many everyday items.
Others uses are in the production of chlorates, chloroform, carbon tetrachloride, and in the bromine extraction.
Chlorine (Gr χλωρος, greenish yellow) was discovered in 1774 by Carl Wilhelm Scheele, who mistakenly thought it contained oxygen. Chlorine was given its name in 1810 by Humphry Davy, who insisted that it was in fact an element.
In nature it is only found combined with other elements chiefly sodium in the form of common salt (NaCl), but also in carnallite, and sylvite.
There are two principal stable isotopes of chlorine, of mass 35 and 37, found in the relative proportions of 3:1 respectively,
giving chlorine atoms in bulk an apparent atomic weight of 35.5. Chlorine has 9 isotopes with mass numbers ranging from 32 to 40. Only three of these isotopes occur naturally: stable Cl-35 (75.77%)and Cl-37 (24.23%), and radioactive Cl-36. The ratio of Cl-36 to stable Cl in the environment is about 700 E -15 : 1. Cl-36 is produced in the atmosphere by spallation of Ar-36 by interactions with cosmic ray protons. In the subsurface environment, Cl-36 is generated primarily as a result of neutron capture by Cl-35 or muon capture by Ca-40. Cl-36 decays to S-36 and to Ar-36, with a combined half-life of 308,000 years. The half-life of this hydrophilic nonreactive isotope makes it suitable for geologic dating in the range of 60,000 to 1 million years. Additionally, large amounts of Cl-36 were produced by irradiation of seawater during atmospheric detonations of nuclear weapons between 1952 and 1958. The residence time of Cl-36 in the atmosphere is about 1 week. Thus, as an event marker of 1950s water in soil and ground water, Cl-36 is also useful for dating waters less than 50 years before the present. Cl-36 has seen use in other areas of the geological sciences, including dating ice and sediments.
Chlorine irritates respiratory systems especially in children and the elderly.
In its gaseous state it irritates mucous membranes and when a liquid it burns skin. It takes as little as 3.5 ppm to be detected as distinct odor but it takes 1000 ppm or more to be fatal. Because of this, chlorine was one ot the gases used during World War I as a war gas.
Exposure to this gas should therefore not exceed 0.5 ppm (8-hour time-weighted average - 40 hour week.).
Acute exposure to high (but non-lethal) concentrations of Chlorine can result in Pulmonary Edema, or fluid in the lungs, an extremely unpleasant condition. Chronic low-level exposeure weakens the lungs, increasing susceptibility to other lung disorders.
Toxic fumes may be produced when bleach is mixed with urine, ammonia or another cleaning product. These fumes consist of a mixture of chlorine gas and nitrogen trichloride; therefore these combinations should be avoided.
See also: Chlorofluorocarbon