Some substances are given below
$$ \begin{aligned} & \mathrm{Ag}, \mathrm{CO}_2(s), \mathrm{SiO}_2, \mathrm{ZnS} \\ & \mathrm{SO}_2(s), \mathrm{AlN}, \mathrm{HCl}(\mathrm{~s}), \mathrm{H}_2 \mathrm{O}(\mathrm{~s}) \end{aligned} $$
The number of molecular solids and network solids in the above list is respectively.
The diffraction pattern of crystalline solid gave a peak at $20=60^{\circ}$. What is the distance ( in cm ) between the layers which gave this peak?
( $\lambda$ of $X$-rays is $1.54 \mathring{A}$ ) $\left(\sin 30^{\circ}=0.5, \sin 60^{\circ}=0.866 ; n=1\right)$
(a) $8.89 \times 10^{-8}$An element crystallising in fcc lattice has a density of $$8.92 \mathrm{~g} \mathrm{~cm}^{-3}$$ and edge length of $$3.61 \times 10^{-8} \mathrm{~cm}$$. What is the atomic weight of element? $$\left(N=6.022 \times 10^{23} \mathrm{~mol}^{-1}\right)$$