Platinum crystallize in a face centered cube crystal with a unit cell length of `3.9231 Å`. The density and atomic radius of platinum are respectively: [Atomic mass of Pt = 195]

Options

A. `45.25 g cm^(-3), 2.516 Å`
B. `21.86 g cm^(-3), 1.387 Å`
C. `29.46 g cm^(-3), 1.48 Å`
D. None of these

Answer

B

Explanation

Density =`(ZxxM)/(N_Axxa^3)=(4xx195)/(6.02xx10^23xx(3.9231xx10^(-8))^3) =21.86 g//cm^3`
for f c c lattice , 4r=`asqrt2`
so, `r=(asqrt2)/4=(3.921sqrt2)/4Å` =1.387 Å