cupric vs cuprous

cupric

adj
  • Containing copper with an oxidation number of 2 

  • Of, pertaining to, or derived from, copper; containing copper. 

cuprous

adj
  • Containing copper with an oxidation number of 1. 

  • Of, or of the nature of, copper. 

How often have the words cupric and cuprous occurred in a corpus of books? (source: Google Ngram Viewer )