At `1425^(@)C` , Fe crystallises in a body-centred cubic lattice whose edge length is `2.93 Ã…` . Assuming the atoms to be packed spheres, calculate :
(a) the radius of the spheres,
(b) the distance between centres of neighbouring spheres,
(c) the number of atoms of Fe per unit lattice and
(d) the total volume occupied by an atom of Fe.

Explanation

(a) `asqrt(3)=4r` where, a=edge length
`r=(asqrt(3))/(4)=(2.93xxsqrt(3))/(4)=1.268 Ã…`
(b) Distance between the centres of neighouring spheres `=2r = 2 xx 1.1268=2.537 Ã…`
(c) No. of atoms per unit cell `=8xx(1)/(8)+1=2`
(d) Volume occupied by an atom of iron `=(4)/(3)pir^(3)`.