A sample of mettallic element X, weighting 3.177g, combines with 0.6015 L of O2 gas ( at normal pressure and 20.0 C) to form the metal oxide with the formula XO. If the density of O2 gas under these conditions is 1.330 g/L, what is the masss of this oxygen? What is the atomic weight of X? What is the identity of X?