Question

Read the given statements carefully.
I. The ionic crystal of AgBr shows both Schottky and Frenkel defect.
II. The unit cell having crystal parameters, $a$ $=$ $b$ $\ne$ $c$, $\alpha$ $\beta$ $={90}^o$, ${\rm Y}$ = ${120}^o$ is hexagonal.
III. In ionic compounds having Frenkel defect, the radius ratio $\frac{r_{+}}{r_{-}}$ is high.
IV. The coordination number of $N{a}^{+}$ ion in NaCl is 4.
The correct statements are

• A. I and II only
• B. II and III only
• C. III and IV only
• D. II, III and IV only

Answer 1

The correct option is A I and II only

The ionic crystal of AgBr can show both Schottky and Frenkel defect.

Parameters for hexagonal crystals are $a=b\ne c$, $\alpha =\beta ={90}^o$, $\gamma ={120}^o$

Frankel defects do not change the radius ratio because the charge neutrality is maintained.

The coordination number of $N{a}^{+}$ ion in NaCl is 6.
I & II are correct.