An Overview about the Chemical Element Chlorine


Symbol: Cl

Atomic Number: 17

Atomic Mass: 35.4527 amu (atomic mass units)

Melting Point: minus 100.98 C (172.17 K, minus 149.764 F)

Boiling Point: minus 34.6 C (238.55 K, minus 30.279997 F)

Number of Protons: 17

Number of Electrons: 17

Number of Neutrons: 18

Classification: Non-Metal

Group Name: Halogen

Crystal Structure: Orthorhombic

Density @ 293 K: 0.003214 grams per cubic centimeter

Color: green/yellow

When the Swedish chemist William Scheele first produced chlorine in 1774 he thought the gas he had formed also contained oxygen. The chlorine gas had been made by combining hydrochloric acid with the mineral ore pyrolusite (MnO2). In 1802 the British chemist Sir Humphry Davy proved that chlorine was an element rather than a mixture of gases. Chlorine gets its name from the Greek word meaning greenish yellow “chloros”.

Chorine is a highly reactive element and will combine to form compounds with most other elements. The element, therefore, is never found free in nature. This is fortunate as chorine is a toxic gas and is lethal if inhaled at concentrations in excess of 1000 parts per million. The gas will burn exposed skin and irritate the mucous membranes. The toxic properties of chlorine led to it being used as the first poisonous gas deployed in a battlefield. The Germans released the gas against the French lines at Ypres on April 22 1915 with devastating and terrifying effects on the French and Algerian troops. Irritant gas weapons had been used before but this was the first use of a potentially lethal gas. Humans can detect chlorine in the atmosphere by smell at concentrations as low as 3.5 parts per million.

There are two stable isotopes of chlorine that are found naturally. These isotopes are in, order of abundance, chlorine-35 (75.77%) and chlorine-37 (24.33%). There are a number of unstable isotopes of chlorine; they have mass numbers that range from 28 to 51. The isotope chlorine-29 has the shortest half-life at less than twenty nanoseconds.

Industrial production of chlorine is carried out by the electrolysis of aqueous sodium chloride solutions. Chlorine solutions are used as antiseptics and disinfectants. As disinfectants they are used in the processing of potable water and to keep swimming pools free of pathogenic bacteria.

They are a number of industrial processes that use chlorine. It plays an important part in the production of paper, plastics, dyes, textiles, medicines, insecticides, solvents and paints.

Numerous compounds of chlorine are of use. The most common of these is sodium chloride (NaCl) or table salt. Other compounds include hydrochloric acid (HCl), chloroform (CHCl3) and carbon tetrachloride (CCl4),