Chlorine is a greenish-yellow gas with atomic number 17 and symbol Cl. It is heavier than air and has strong oxidizing properties. Chlorine is produced industrially by electrolysis of aqueous sodium chloride and is used as a disinfectant and bleaching agent. It is toxic and corrosive, causing lung damage in high concentrations. Chlorine is essential for human life in the form of chloride ions.
Chlorine is an element with atomic number 17 in the periodic table and chemical symbol Cl. It is a greenish-yellow gas with a boiling point of -29°F (-34°C) at normal atmospheric pressure and a freezing point of -151°F (-101.5°C). Natural chlorine consists almost entirely of the two stable isotopes, chlorine-35 and chlorine-37, which give it an atomic weight of 35.4527. Among the other important physical properties of chlorine is the fact that it is heavier than air and if released into the environment it tends to collect in low-lying areas. Chlorine is a member of group 17 of the periodic table, which also contains fluorine, bromine, iodine and astatine, collectively known as halogens.
Within the group of halogens, in order of increasing atomic weight, this element is found between fluorine and bromine. The chemical properties of chlorine resemble those of the other halogen elements. It has seven electrons in its outermost shell and is very electronegative; therefore it has a strong tendency to attract electrons from other atoms, making it a powerful oxidizing agent. The electronegativity decreases with increasing atomic weight within the halogen group. Chlorine is therefore less electronegative than fluorine, but more than bromine: it will replace bromine by its compounds: 2NaBr + Cl2 -> 2NaCl + Br2.
Elemental chlorine exists as molecules made up of two chlorine atoms held together by a single covalent bond. Most chlorine compounds have the element in its -1 oxidation state, where it accepts an electron from another atom; however, when combined with the more electronegative elements oxygen and fluorine it has a positive oxidation state, which for oxides can be +1, +3, +4, +5 or +7. Oxygen and chlorine do not combine directly, but chlorine oxides and compounds containing the anions hypochlorite (OCl-), chlorite (ClO2-), chlorate (ClO3-), and perchlorate (ClO4-) can be produced indirectly. Chlorine readily forms ionic bonds with metals, where it accepts an electron from the metal, resulting in a chloride ion (Cl-) with an oxidation state of -1, such as sodium chloride (NaCl) or common salt.
Hydrogen gas combines easily with chlorine to form hydrochloric acid (HCl); the reaction is explosive in the presence of sunlight. It is quite soluble in water, dissolving to produce a mixture of hydrochloric acid, hypochlorous acid and dissolved chlorine. Ammonia combines with chlorine to form the toxic compounds monochloramine and dichloramine, or the highly shock-sensitive explosive nitrogen trichloride, depending on relative proportions. For this reason household cleaning products containing chlorine should never be mixed with those containing ammonia. Chlorine reacts readily with many organic compounds and organic chlorides are important in the manufacture of plastics such as polyvinyl chloride (PVC) and as non-flammable solvents.
Although it is a common element in the earth’s crust, found in a number of minerals, such as halite (NaCl), the reactive properties of chlorine are such that it does not occur naturally in an uncombined state. Chlorine is produced industrially mainly by the electrolysis of aqueous sodium chloride. This also produces sodium hypochlorite (NaOCl) solution, better known as household bleach. The element is also a byproduct of the production of metallic sodium by the electrolysis of molten sodium chloride. In the laboratory it can be produced in various ways, for example by the reaction of calcium hypochlorite with an acid.
In the form of chloride ions, chlorine is essential for human life; however, elemental chlorine is toxic and corrosive. It has an unpleasant, suffocating odor and irritates the respiratory tract if inhaled. In high concentrations it causes lung damage which can be fatal, and the gas was used as a chemical weapon by the German Army during World War I. The oxidizing properties of chlorine make it a useful disinfectant and bleaching agent. Compounds that release small amounts of chlorine are used to sterilize drinking water and swimming pools and are included in various cleaning products.
Protect your devices with Threat Protection by NordVPN
