Q 21: Gold (atomic radius = 0.144 nm) crystallises in a face–centred unit cell. What is the length of a side of the cell?

Q 21: Gold (atomic radius = 0.144 nm) crystallises in a face–centred unit cell. What is the length of a side of the cell?

Solution:

Given that

Radius of atom R= 0.144 nm

For a face–centered unit cell

Edge a = 2√2 R

Plug the values we get 

Edge a= 0.144 x 2 x 1,414 nm

Edge a= 0.407 nm

Solution: :– The length of a side of the cell = 0.407 nm