Given: Molar mass of $\mathrm{Fe}$ and $\mathrm{O}$ is 56 and $16 \mathrm{~g} \mathrm{~mol}^{-1}$ respectively. $\mathrm{N}_{\mathrm{A}}=6.0 \times 10^{23} \mathrm{~mol}^{-1}$

A metal M forms hexagonal close-packed structure. The total number of voids in 0.02 mol of it is _________ $$\times$$ $$10^{21}$$ (Nearest integer).

(Given $$\mathrm{N_A=6.02\times10^{23}}$$)

Ionic radii of cation $$\mathrm{A}^{+}$$ and anion $$\mathrm{B}^{-}$$ are 102 and $$181 \,\mathrm{pm}$$ respectively. These ions are allowed to crystallize into an ionic solid. This crystal has cubic close packing for $$\mathrm{B}^{-}$$. $$\mathrm{A}^{+}$$ is present in all octahedral voids. The edge length of the unit cell of the crystal AB is __________ pm. (Nearest Integer)

Metal $$\mathrm{M}$$ crystallizes into a fcc lattice with the edge length of $$4.0 \times 10^{-8} \mathrm{~cm}$$. The atomic mass of the metal is ____________ $$\mathrm{g} / \mathrm{mol}$$. (Nearest integer)

$$\left(\right.$$ Use : $$\mathrm{N}_{\mathrm{A}}=6.02 \times 10^{23} \mathrm{~mol}^{-1}$$, density of metal, $$\mathrm{M}=9.03 \mathrm{~g} \mathrm{~cm}^{-3}$$ )