Hypothetical metal M has a molecular weight 152g/mol and crystallizes in a body-centered cubic array of atoms in which the length of the unit cell's edge is 541.8 pm (10-12 m ). Calculate the density of the metal in g/cm3 Answer: Ar is a solid below 189C with a face-centered cubic array of atoms and a supposed density of 2.39g/cm3. Assuming that the atoms are spheres in contact along the face diagonal, what is the radius of a Ar atom (in Angstroms)? An angstrom =1010m or 108cm. Hint, first find the length of an edge of the unit cell. (Argon's actual density is 1.65g/cm3.)