What is the charge on cation formed from the following elements? For those elements that form more than one cation, indicate the ionic charges most commonly observed.
1. Gallium
Express your answer as an ion(s) separated by a comma.
2.Nickel
Express your answer as an ion(s) separated by a comma.
3.Copper
Express your answer as an ion(s) separated by a comma.
4.Strontium
Express your answer as an ion(s) separated by a comma.