An element occurs in two crystalline form `alpha` and `beta`. The `alpha`-from has an `fcc` with `alpha = 3.68 Å` and `beta`-from has a `bcc` with `a = 2.92 Å`. Calculate the ratio of their densities.

Options

A. 1
B. 2
C. 3
D. 4

Explanation

`Z_(eff)` for fcc=4,`Z_(eff)` for bcc=2
Atomic volume of `alpha-`form
`=((3.68xx10^(-8))^(3)xxN_(A))/(4)`
Atomic volume of `beta-`form
`((2.92xx10^(-8))^(3)xxN_(A))/(2)`
(As Aw is same, element is same), so the density ratio is
`rho_(alpha):rho_(beta)=v_(beta),v_(alpha)=((2.92)^(3))/(2),((3.68)^(3))/(4)=12.448:12.459=1:1`