Chlorine
Chlorine, the seventeenth element, is a halogen with an atomic mass of 35.4527. It is
very active, and has a valence of -1. Cl's electron levels are 2-8-7. Chlorine, a gas, was
discovered in 1774 by C. W. Scheele of Sweden. It melts at 172.17 K, and boils at 239.18 K.
Chlorinated hydrocarbons such as DDT were used as pesticides in the mid 20th century. A single atom of
chlorine can destroy hundreds or even thousands of ozone molecules, contributing to the hole in the
ozone layer over Antarctica. Bacause of this, the use of chlorofluorocarbons (CFC's) has been banned.
Chlorine is poisonous, and chlorine dioxide is explosive at concentrations above 10%, or temperatures above
266 degrees F. Chlorine is a greenish yellow gas, with an irritating odor. Contact with Cl can severely burn eyes
and skin, can cause pulmonary edema, and can damage teeth. Cl can be detected at 3.5 ppm, and is fatal at 1000 ppm.
Cl is a highly electronegative element, with an electronegativity of 3.98.
Cl's electron configuration is [Ne]3s2p5.
Cl has a density of 3.214 g/L at STP.
June 18, 1997, updated August 7, 1998
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