Calculate the atomic mass of an element X if it has 3 naturally occurring isotopes: X-20 with an abundance of 90.51% and a mass of 19.992, X-21 with an abundance of 0.27% and a mass of 20.994, and X-22 with an abundance of 9.22% and a mass of 21.991. Using the calculated mass, which element is this likely to be? this is the last question so plz help me