Chlorine (Z=17): The Key Element in the Chemical Industry and Disinfection
Essential Role of Chlorine
Chlorine (symbol Cl, atomic number 17) is a widely used chemical element in various industries, particularly in the production of plastics, solvents, and water disinfection. It is also a key element in the synthesis of many chemical products.
Contribution of Chlorine in Industrial Processes
Chlorine is commonly used in the production of PVC (polyvinyl chloride), in the treatment of drinking water and wastewater, and in the manufacture of pharmaceuticals and agrochemicals. Additionally, it is involved in large-scale chemical processes such as solvent production and hygiene products.
History of Discovery
1774: Discovery by Carl Wilhelm Scheele Chlorine was first discovered by the Swedish chemist Carl Wilhelm Scheele, who isolated it from hydrochloric acid, naming it "dephlogisticated muriatic acid".
1810: Identification by Humphry Davy The British chemist Humphry Davy isolated chlorine in its elemental form and confirmed its chemical nature.
Atomic Structure
Constitution: The chlorine atom has 17 protons, 18 neutrons, and 17 electrons, with an electron configuration of 1s² 2s² 2p⁶ 3s² 3p⁵. Isotopes:
Chlorine-35 (³⁵Cl): stable isotope, representing approximately 75% of natural chlorine.
Chlorine-37 (³⁷Cl): stable isotope, representing approximately 25% of natural chlorine.
Physical Properties
Diatomic gas (Cl₂), yellow-green, with a strong irritating odor.
Molar mass: 35.45 g/mol
Melting point: 171.6 K (-101.6 °C)
Boiling point: 239.11 K (-34.04 °C)
Density: 3.214 g/L (at 0°C and 1 atm)
Toxic and corrosive gas, particularly dangerous at high concentrations.
Chemical Reactivity
Chlorine is a highly reactive gas and readily reacts with many elements, including metals and non-metals.
It reacts vigorously with hydrogen to form hydrogen chloride (HCl).
Chlorine is used in the production of organochlorine compounds, such as pesticides and plastics.
It is also involved in disinfection reactions, particularly in water treatment plants.
Industrial and Technological Applications
Production of PVC (polyvinyl chloride), widely used in the construction and industrial sectors.
Used in water treatment to eliminate pathogens and make water potable.
Manufacture of organochlorine solvents and pharmaceuticals.
Used in the production of industrial chemicals such as detergents and disinfectants.
Employed in industrial processes for the production of chlorine gas, used as a powerful oxidizing agent.
Biological and Ecological Role
Chlorine plays a crucial role in disinfection systems but can be toxic to living organisms at high concentrations.
It is present as chloride ions (Cl-) in many biological systems, playing a role in acid-base balance.
Water chlorination is an effective method to prevent the spread of infectious diseases in at-risk areas.
Environmental and Industrial Challenges
Chlorine is a toxic gas, and its excessive use can lead to environmental and health risks, including the formation of dioxins, which are pollutants and potentially carcinogenic substances.
Managing chlorinated pollution, particularly organochlorine compounds, remains a major environmental challenge.
Water treatment plants must use alternative methods to minimize the ecological impacts associated with water chlorination.
