text: This element is the most widespread catalyst of the azide-alkyne cycloaddition.
full_question: This element is the most widespread catalyst of the azide-alkyne cycloaddition. Salts of this element catalyze the reaction of diazonium salts into aryl halides in the Sandmeyer reaction. A brick-red oxide of this element is created as a precipitate to indicate the presence of reducing sugars in Benedict’s test. This element, which produces a blue-green color in a flame test, forms the green surface layer verdigris when exposed to air for long periods of time. For 10 points, name this element that, with tin, forms the alloy bronze.
first_sentence: This element is the most widespread catalyst of the azide-alkyne cycloaddition.