Chlorine

PSM V31 D740 Carl Wilhelm Scheele

Chlorine liquid in an ampoule

Die chemischen elemente cl

DCl Neutron powder

Nickel(II)-chloride-hexahydrate-sample

Chlorine is a chemical element with the symbol Cl and atomic number 17. Positioned in group 17 of the periodic table, chlorine is a halogen and is the second lightest halogen following fluorine. The element forms diatomic molecules under standard conditions, known as dichlorine (Cl₂).

Properties

Chlorine is a yellow-green gas at room temperature. 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, just behind oxygen and fluorine. This reactivity is due to the high electronegativity of chlorine and the fact that it can gain an electron to form the chloride ion (Cl⁻).

Production

The most common method of producing chlorine is through the electrolysis of sodium chloride solutions in a process known as the Chloralkali process. This process also produces sodium hydroxide (caustic soda) and hydrogen gas as by-products.

Applications

Chlorine has a wide range of applications. It is used extensively for water purification, in the manufacture of disinfectants and in swimming pools to keep the water free from bacteria and other pathogens. In the chemical industry, chlorine is used in the production of a wide range of products, including plastics, pesticides, and pharmaceuticals. Chlorine is also used in the production of bleach, which is used both domestically and industrially for whitening clothes, removing stains, and as a disinfectant.

Health and Environmental Effects

Exposure to chlorine gas can be harmful to human health. Inhalation of chlorine gas can cause difficulty breathing, chest pain, cough, and irritation of the eyes, nose, and throat. At high concentrations, chlorine gas can be lethal. Due to its high reactivity, chlorine can also react with organic matter in the environment to form chlorinated compounds, some of which can be toxic and contribute to environmental pollution.

Safety

Due to its toxic and reactive nature, the handling and storage of chlorine require strict safety measures. This includes the use of appropriate protective equipment and the implementation of safety protocols to prevent accidental exposure.

History

Chlorine was first isolated in 1774 by Swedish chemist Carl Wilhelm Scheele, who mistakenly thought it contained oxygen. Its true nature was not understood until 1810, when Sir Humphry Davy proved it to be an element and named it chlorine, from the Greek word 'chloros', meaning greenish-yellow.