Sodium metal crystallizes in a body centred cubic lattice with unit cell edge length of $$4~\mathop A\limits^o $$. The radius of sodium atom is __________ $$\times ~10^{-1}$$ $$\mathop A\limits^o $$ (Nearest integer)

An atomic substance A of molar mass $$12 \mathrm{~g} \mathrm{~mol}^{-1}$$ has a cubic crystal structure with edge length of $$300 ~\mathrm{pm}$$. The no. of atoms present in one unit cell of $$\mathrm{A}$$ is ____________. (Nearest integer)

Given the density of $$\mathrm{A}$$ is $$3.0 \mathrm{~g} \mathrm{~mL}^{-1}$$ and $$\mathrm{N}_{\mathrm{A}}=6.02 \times 10^{23} \mathrm{~mol}^{-1}$$

Number of crystal systems from the following where body centred unit cell can be found, is ____________.

Cubic, tetragonal, orthorhombic, hexagonal, rhombohedral, monoclinic, triclinic

A metal M crystallizes into two lattices :- face centred cubic (fcc) and body centred cubic (bcc) with unit cell edge length of $$2.0$$ and $$2.5\,\mathop A\limits^o $$ respectively. The ratio of densities of lattices fcc to bcc for the metal M is ____________. (Nearest integer)