C. 2,500Dg Im pretty sure thats it
3Ba + N2 -----> Ba3N2
Ba is in the second group and metal, its charge = +2 in the compound.
N is non-metal, it is in 15th group, so it has 5 electrons on the last level, so it can take 3 electrons more(8-5=3). N has charge (-3) in compound.
Ba and N form compound Ba3N2.