<Tr> <Th_colspan="2"> Related compounds </Th> </Tr> <Tr> <Td> Other anions </Td> <Td> Copper (I) sulfide Copper (II) sulfide Copper (I) selenide </Td> </Tr> <Tr> <Td> Other cations </Td> <Td> Copper (II) oxide Silver (I) oxide Nickel (II) oxide Zinc oxide </Td> </Tr> <Tr> <Td_colspan="2"> Except where otherwise noted, data are given for materials in their standard state (at 25 ° C (77 ° F), 100 kPa). </Td> </Tr>

How can you prove that red oxide of copper is not an element