Period 3 element in 1810, who named it chlorine, from the Greek word χλωρος (chlōros), meaning "green-yellow." Chlorine is a component of various compounds, including table salt. It is the second most abundant halogen and 21st most abundant chemical element in Earth's crust. The great oxidizing potential of chlorine led it to its bleaching and disinfectant uses, as well as uses of an essential reagent in the chemical industry. As a common disinfectant, chlorine compounds are used in swimming pools to keep them clean and sanitary. In the upper atmosphere, chlorine-containing molecules such as chlorofluorocarbons have been implicated in ozone depletion. "Argon" (symbol
William Crookes was devoted mainly to independent work. In 1859, he founded the "Chemical News", a science magazine which he edited for many years and conducted on much less formal lines than was usual for the journals of scientific societies. In 1861, Crookes discovered a previously unknown element with a bright green emission line in its spectrum and named the element thallium, from the Greek "thallos", a green shoot. Crookes wrote a standard treatise on "Select Methods in Chemical Analysis" in 1871. Crookes was effective in experimentation. The method of spectral analysis, introduced by Bunsen and Kirchhoff, was received by Crookes with