Question

The radius of silver atom is 143.5 pm and it crystallises in face centred cubic arrangement. (Atomic mass of Ag = 107.47, N_A = 6.023 × 10²³)

What is the edge length of the unit cell?

Options

• 405.8 pm

• 40.6 pm

• 331.4 pm

• 287 pm

Answer 1

405.8 pm

Explanation:

Given: Radius of silver atom (r) = 143.5 pm

Face-centred cubic (fcc) Structure,

`a = (4 r)/sqrt 2`

∴ `a = (4 xx 143.5)/sqrt 2`

= `574/1.414`

= 405.8 pm