A sample of metallic elemnt X, weighing 3.77 grams, combines with 0.615L of 02( at normaal pressure and 20 degree C) to form metal oxide with the formula XO. If the density of )2 gas under these conditions is 1.330 g/L, what is the mass of this oxygen? The atomis oxygen is 15.9994 amu. What is the atomic weight of X?