Simplify the following text for a Grade 5 native English-speaking person.
Original: Both cuprous and cupric oxides are known : Copper ( I ) oxide ( cuprite ) and copper ( II ) oxide ( tenorite ) . Among the numerous copper sulfides , important examples include copper ( I ) sulfide ( chalcocite ) and copper ( II ) sulfide ( covellite ) .
Simplified: This is because of a coating of copper ( II ) oxide .