a. The unit cell is the smallest group of atom which have overall symmetry of a crystal, and from which is the entire letters can be buled built up by repetition in 3 dimensions.
b. The volume(v) of the unit cell is equal to the cell edge length (a)cubed.
c. density of polonium is 9.32g/cm3.
no it is not possible, because they both have the same number of valence electrons in each element. in a compound you are supposed to have two or more elements that have different numbers of valence electrons so when put together they for a compound.