The edge length of $fcc$ type unit cell of copper having atomic radius $127.6 \ pm$ is equal to (in $pm$)

Niobium crystallizes in a $bcc$ structure. If its density is $8.55 \, g/cm^3$, calculate the atomic radius of niobium. [Atomic mass of $Nb = 93 \, u$] (in $pm$)

Potassium metal crystallizes in a face-centered cubic $(FCC)$ lattice. If the edge length of the unit cell is $0.574 \ nm$,what is the shortest distance between any two potassium nuclei (in $nm$)?

$KBr$ has a rock salt type structure and has a density of $3.70 \ g/cm^3$. The edge length of the unit cell is approximately [molecular weight of $KBr = 120 \ g/mol$]:

Calculate the number of atoms present in a unit cell of an element having molar mass $190 \ g \ mol^{-1}$ and density $20 \ g \ cm^{-3}$. Given that $[a^3 \cdot N_A = 38 \ cm^3 \ mol^{-1}]$.

In a body-centred cubic $(bcc)$ lattice of potassium,the correct relation between the atomic radius $(r)$ of potassium and the edge-length $(a)$ of the cube is: