A given metal crystallises out with a cubic structure having edge length of 361 pm. If there are four metal atoms in one unit cell, what is the radius of one atom?
- 80 pm
- 108 pm
- 40 pm
- 127 pm
Answer
(4) 127 pm
Solution
Four atoms per cubic unit cell ⇒ face-centred cubic (fcc) lattice.
∵ In fcc, atoms touch along the face diagonal: 4r = 2 a
⇒ r = a2 2
= 3612 1.414 pm
= 3612.828 pm
127.6 pm 127 pm
Answer: (4)