Task: Text Categorization
Input (English): The Fraunhofer lines of the Sun's electromagnetic spectrum contain a D-line, sometimes known as a ""doublet,"" produced by transitions in this element's family but traditionally named after this element. This metal is currently made using the Downs Cell. When it is used as a coolant in nuclear reactors, the radioactive 24 isotope of this element is formed. It produces a bright (*) yellow flame when heated. This is the second-lightest alkali metal after lithium. For 10 points, identify this metal whose chloride is table salt.
Output (English): Science