1)The element nickel has ccp packing with a face-centered cubic unit cell. The density of nickel is 8900 kg/m3 and the cell volume is 4.376 x 10-23 cm3. Calculate the value of Avogadro's number to three significant figures based on these data. (Note: the value may differ from the tabular value).

Question

2)

Answer 1

The cell volume is given, the density is given, mass of unit cell = volume x density.

mass of atom = atomic mass/N where N = Avogadro's number. There are 4 atoms to the unit cell; therefore,
Mass of unit cell = 4*atomic mass/N.
Solve for N

Answer 2

is it always 4 atoms in a unit cell