cuprous

/ˈkjuːprəs/
adjective
  1. Containing or relating to copper, especially in its +1 oxidation state (as opposed to cupric, which is +2).
    • The mineral cuprite is a cuprous oxide that has a deep red color.
    • In chemistry class, we learned that cuprous compounds often form when copper reacts with certain acids.
    • The old statue had a green patina, but underneath it was made of cuprous metal.
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