An element crystallizes in a body-centred cubic $(BCC)$ structure with an edge length of $400 \ pm$. Calculate the interatomic distance in the crystal. Additionally, if an atom has a radius of $300 \ pm$ and crystallizes in a face-centred cubic $(FCC)$ lattice, calculate the distance between the nearest neighbours.

Atoms of metals $x$,$y$,and $z$ form face-centred cubic $(fcc)$ unit cell of edge length $L_x$,body-centred cubic $(bcc)$ unit cell of edge length $L_y$,and simple cubic unit cell of edge length $L_z$,respectively. If $r_z = \frac{\sqrt{3}}{2} r_y$; $r_y = \frac{8}{\sqrt{3}} r_x$; $M_z = \frac{3}{2} M_y$ and $M_z = 3 M_x$,then the correct statement$(s)$ is (are) [Given: $M_x$,$M_y$,and $M_z$ are molar masses of metals $x$,$y$,and $z$,respectively. $r_x$,$r_y$,and $r_z$ are atomic radii of metals $x$,$y$,and $z$,respectively.]
$(A)$ Packing efficiency of unit cell of $x >$ Packing efficiency of unit cell of $y >$ Packing efficiency of unit cell of $z$
$(B)$ $L_y > L_z$
$(C)$ $L_x > L_y$
$(D)$ Density of $x >$ Density of $y$

Which of the following is incorrectly matched?

Calculate the number of atoms present in $1.625 \text{ g}$ of a metal that forms a $bcc$ unit cell structure. Given: $[\rho \times a^3 = 3.25 \times 10^{-22} \text{ g}]$.

Which one of the following statements is not correct?

Which of the following is the correct cooling curve for an amorphous solid?