Experimentally it has been found that nickel has a density of 8,9 gcm-3 and that radius of its atom is 1,25 Å. Determine which type of cubic crystal lattice does nickel crystalize in.
I don't know how to approach the problem because I cannot get a hang of how to calculate side of the unit cell. I know that it cannot possibly be cP (primitive) for the reason that the only metal that crystalizes in that crystal lattice is α-polonium. for that sake, it remains only cI or cF, but in both of these the relationship between radius and length of the side is differently expressed; cF: a=2√(2)r, cI: a=(4√(3)r)/(3)