text: This element is used to reduce nitrogen oxides to elemental nitrogen in CHN analyzers.
full_question: This element is used to reduce nitrogen oxides to elemental nitrogen in CHN analyzers. Indium, gallium, selenium, and this element make up a common thin-film solar cell. Plastocyanin and azurin are members of a class of redox-performing proteins which have "blue centers" named for this element. This element's chloride is used to regenerate the palladium chloride catalyst used to oxidize ethylene to acetaldehyde in the Wacker process. This element is in the +1 oxidation state in a catalyst used to form aryl halides from diazonium salts. This element and lithium are found in a class of compounds which selectively performs 1,4-conjugate additions to carbonyls. This element gives off a blueish-green color in the flame test, and it is used in the Sandmeyer reaction and Gilman reagents. For 10 points, name this element which forms an alloy with tin called bronze.
first_sentence: This element is used to reduce nitrogen oxides to elemental nitrogen in CHN analyzers.
raw_answer: copper