Ca2+ would bond to any element in a 1 to 1 ratio that had an equal and opposite charge.
Neon is a noble gas, and doesn’t form bonds m
Carbon isn’t typically found in ion state, but if it did, it would likely by C4+
Flouring in ionic state is F1-, so you would need 2 flourines to cancel the 2+ charge of Calcium
Then the only option left would be Oxygen which, when in ion form is found be 2-
