Question

Palladium crystallizes with a face-centered cubic structure. It has a density of 12.0 g/cm^3, a radius of 138 pm, and a molar mass of 106.42 g/mol.

Use these data to estimate Avogadro's number.

Answer 1

The fcc has 4 atoms/unit cell.
You know r, use that to calculate the edge of the unit cell, a.
4r = a(2)^1/2
Then a³ = volume of the unit cell.
mass of unit cell = volume x density.
Then mass of unit cell is
4 atoms x 106.24/N = mass
Calculate N.

Answer 2

I got lost. :( I got:

a=390

...and when I cubed that, I got a number that was too big so I figured that was wrong. What did I do wrong?