Silver (atomic weight $= 108 \ g \ mol^{-1}$) has a density of $10.5 \ g \ cm^{-3}$. The number of silver atoms on a surface of area $10^{-12} \ m^2$ can be expressed in scientific notation as $y \times 10^x$. The value of $x$ is

Which of the following statements is correct?

Give the correct order of initials $T$ (true) or $F$ (false) for the following statements:
$I.$ In an anti-fluorite structure,anions form $FCC$ lattice and cations occupy all tetrahedral voids.
$II.$ If the radius of cations and anions are $0.2 \ \mathring{A}$ and $0.95 \ \mathring{A}$,then the coordination number of the cation in the crystal is $4$.
$III.$ An atom/ion is transferred from a lattice site to an interstitial position in a Frenkel defect.
$IV.$ The density of a crystal always increases due to a substitutional impurity defect.

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.

Which of the following is incorrectly matched?

$A$ mixture of $KCl$ and $KF$ is added to sodium chloride.