Chlorine (from the
Greek language χλωρóς chloros, meaning "pale
green"), is the
chemical element with
atomic number 17 and symbol Cl. It is a
halogen, found in the
periodic table in
group 17. As the
chloride ion, which is part of
common salt and other compounds, it is abundant in
nature and necessary to most forms of life, including
humans. In its elemental form, it is a pale green
gas about 2.5 times as dense as air. It has a
disagreeable suffocating odor and is
poisonous. Chlorine is a powerful
oxidant and is used in
bleaching and disinfectants.