The density of aluminum is 2.7 g/cm³ and that of Al2O3 is about 4 g/cm³. Describe the characteristics of the aluminum-oxide film. Compare these with the oxide film that forms on tungsten. The density of tungsten is 19.254 g/cm³ and that of WO3 is 7.3 g/cm³. (Hint: The Pilling-Bedworth Ratio (PBR) gives the volume of oxide formed to the volume of metal atoms.)
