Chlorine was discovered in 1774 by Scheele by the action of HCl on $MnO_2$. In 1810 Davy established its elementary nature and suggested the name chlorine on account of its colour (Greek, chloros = greenish yellow).
It is a greenish yellow gas with pungent and suffocating odour. It is about 2-5 times heavier than air. It can be liquefied easily into greenish yellow liquid which boils at 239 K. It is soluble in water.
It has great affinity for hydrogen. It reacts with compounds containing hydrogen to form HCl.