The formula for the copper II ion, which is more commonly known as cupric ion, is Cu2+.
Explanation: Copper is a transition metal that can exist in multiple oxidation states, the two most common being +1 and +2. In its +2 oxidation state, copper loses two electrons, which gives it a positive charge of 2. Hence, it is denoted as Cu2+. This ion is often found in various compounds and is significant in many chemical reactions and biological processes.