Gold (atomic mass 197 u) crystallises in a face-centred unit cell. What is its atomic radius if the edge length of the gold unit cell is `0.407 x 10^(-9)`m?

Options

A. 0.115nm
B. 0.144nm
C. 0.235nm
D. 0.156nm

Answer

B

Explanation

Edge length of the God unit cell (a) `=0.407 xx 10^(-7)m`
For FCC unit cell, the atomic radius (r ) `=a//(2 sqrt2)`
`=0.4007 xx 10^(-9)//2 sqrt2`
=0.144nm