Ammonium chloride crystallises in CsCl type (bcc) lattice with unit cell edge length of 387 pm. Distance between oppositely charged ions in the lattice and radius of the `NH_(4)^(+)` ion are respectively (if the radius of `Cl^(-)` ion is 181 pm).

Options

A. 356.12 pm, 175.12 pm
B. 348.23 pm, 167.23 pm
C. 335.15 pm, 154.15 pm
D. 326.35 pm, 145.35 pm

Answer

C

Explanation

(a) In a bcc lattice, oppositely charged ions touch each other along the cross-diagonal of the cube.
So, `2r_(c)+2r_(a)=sqrt(3)a`
`r_(c)=r_(a)=(sqrt(3))/(2)a=(sqrt(3))/(2)xx387=335.15` pm
(b) Given that, `r_(a)=181` pm, `r_(c)=335.15-181.0=154.15` pm.