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
Shades of cyan verdigris was the most vibrant green pigment available and was frequently used in painting. Verdigris was sometimes used to illustrate cyan colors in early color wheels. Viridian is a blue-green pigment, a hydrated chromium(III) oxide, of medium saturation and relatively dark in value. It is composed more of green than blue. Specifically, it is a dark shade of spring green, the color between green and cyan on the color wheel, or, in paint, a tertiary blue–green color. Viridian takes its name from the Latin "viridis", meaning "green". The first recorded use of "viridian" as a color name in English was