Question

The lanthanide metal europium (Eu) forms a crystalline solid with a cubic unit cell of edge length 3.854 Å. The density of europium is 4.408 g cm-3. The crystal structure of solid europium is



a. body-centered cubic

b. simple cubic

c. face-centered cubic

Answer 1

Calculate the mass of a unit cell for each of the three choices. The fcc structure will have the highest mass and density. Note that the atom at each corner of the unit cell is shared by eight cells.

For a simple cubic, the mass of a unit cell of Eu is 152 amu = 3.95*10^-24 g and the density is
2.53*10^-22g/(3.854*10^-8 cm)^3
= 4.42 g/cm^3

That looks like the right answer to me.

Answer 2

UBC wooo go thinderbirds!!