Is this the correct formula for the compound between nitrogen and calcium?
Check valences (oxidation numbers) for Ca which is a plus 2, and the negative valence for Nitrogen is a -3 Next put down the elements, Ca N and over the Ca put its valence of +2 and over the n put its valence of -3. Now ask yourself what is the smallest number that 3 and 2 will divide into. Answer 6. Now the 2 over the Ca goes into 6 three times, so place a subscript 3 just to the right of Ca, and 3 goes into 6 twice, so place a 2 just to the right of the N and you have Ca3N2, called calcium nitride.
