Question

Potassium crystallizes in a body centred cubic lattice.calculate the approximate number of unit cells in 1g of potassium.(Atomic mass of the potassium is 39u)

Answer 1

In BCC unit cell, there are eight atoms at cornes and one atom at body center.
So, total no. of atoms per unit cell = 1/8 x 8 +1 = 2
Now, no, of atoms in 1 gm potassium = 1/39 x 6.022 x 10²³ = 1.54 x 10²² atoms,
So, no. of unit cell in 1g Potassium, = 1.54 x 10²² /2 = 0.77 x 10²²