Question

Each rubidium halide crystallising in the $NaCl$ type lattice has a unit cell length $0.30\stackrel{\circ }{A}$ greater than that for corresponding potassium salt. $(r_{\left(K^{+}\right)}=1.33\stackrel{\circ }{A})$ of the same halogen. Hence, ionic radius of $R{b}^{+}$ is:

• A. $1.18\stackrel{\circ }{A}$
• B. $1.48\stackrel{\circ }{A}$
• C. $1.63\stackrel{\circ }{A}$
• D. $1.03\stackrel{\circ }{A}$

Answer 1

The correct option is B $1.48\stackrel{\circ }{A}$

The unit cell length increases by $0.30\stackrel{\circ }{A}$ in case of rubidium halide crystal.This is due to two atoms present at the corners.

Thus $r_{R{b}^{+}}=1.33+\frac{0.30}{2}\stackrel{\circ }{A}=1.48\stackrel{\circ }{A}$