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
Data element name alternate key, of a Data Elements table of the data dictionary. The data element name typically conforms to ISO/IEC 11179 metadata registry naming conventions and has at least three parts: Many standards require the use of Upper camel case to differentiate the components of a data element name. This is the standard used by ebXML, GJXDM and NIEM. Users frequently encounter ISO/IEC 11179 when they are exposed to XML Data Element names that have a multi-part Camel Case format: The specification also includes normative documentation in appendices. For example the XML element for a person's given (first) name would be