Which element forms stable +2 cations?
quick way is look we’re they are on the periodic table you can tell a little bit about the elements by looking to see what column their in. On the left the first column is +1 the second is +2 and then skip the transition metals to column 13 where Boron is that is +3 This not always this easy. Starting from the right the column 17 Fluorine column is -1, the Oxygen column is -2, and the Nitrogen column is -3. The other columns depend on what their being bonded with.