Page 40 - Curriculum Visions Dynamic Book

Cf see Californium Chlorine (Cl)
Element 17. Chlorine is a greenish-yellow gas and the second lightest halogen in group 7 in the Periodic Table.
Chlorine is never found as a gas in nature. It is an extremely reactive element and a strong oxidising agent. It is very corrosive and poisonous. It is heavier than air and dissolves in water.
Chlorine is most commonly found as the harmless compound NaCl, common salt.
Discovery
Chlorine was discovered in 1774 by Carl Wilhelm Scheele when he poured concentrated hydrochloric acid onto the mineral pyrolusite (manganese dioxide). He thought the gas was an oxide, but the fact
that it was an element
was proved, and the
element was named
by Sir Humphry
Davy in 1810.
 Chlorine gas has a characteristic green colour.
 Rock salt (halite)
is made from sodium chloride.These cubic crystals of halite were formed from the evaporating waters
of a desert lake bed.
Key facts...
Name: chlorine
Symbol: Cl
Atomic number: 17
Atomic weight: 35.45
Position in Periodic Table: group 7 (17)
(halogens); period 3
State at room temperature: gas
Colour: greenish-yellow
Density of gas at 20°C: 2.96 g/cc
Melting point: –101°C
Boiling point: –34°C
Origin of name: from the Greek word chloros,
meaning pale green
Shell pattern of electrons: 2–8–7
40