The substance gray tin is found to crystallize in a cubic lattice, with an edge length of 646.0 pm. if the density of solid gray tin is 5.850 g/cm3, how many sn atoms are there per unit cell?

First find the volume of the cubic lattice given edge length of 646 pm or 6.46x10^-8 cm.

volume = (6.46x10^-8 cm)^3

volume = 2.7x10^-22 cm^3

The total mass of the lattice is:

mass = (5.850 g/cm^3) * 2.7x10^-22 cm^3

mass = 1.577x10^-21 grams

The molar mass of tin is 118.71 g/mol and the Avogadros number is 6.022 x 10^23 atoms/mol, hence:

Sn atoms = [1.577x10^-21 g / (118.71 g/mol)] * 6.022 x 10^23 atoms/mol

Sn atoms = 8 atoms

the volume increases

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.