In an ionic solid `r_((+)) = 1.6 Å and r_((-)) = 1.864 Å`. Use the radius ratio rule to determine the edge length of the cubic unit cell in `Å`

Answer

4

Explanation

`(r_(+))/(r_(-)) = (1.6)/(1.864) = 0.858`
So, it is CsCl type unit cell
So `sqrt3 a = 2 (r_(+) + r_(-))`
So `a = (2(1.864 + 1.6))/(sqrt3) Å = 2 xx 2 Å = 4Å`