Chlorine is a chemical element and thick yellow-greenish gas found naturally in the nature. It is denoted by the chemical symbol CL and its atomic number is 17.

It was discovered in 1774 by the German-Swedish pharmaceutical chemist Carl Wilhelm Scheele. He treated a mineral pyrolusite with HCL and observed an unknown gas hitherto produced which he named as “dephlogisticated muriatic acid” (chlorine). It helps to kill bacteria. It is used to purify the water.