An element $\mathrm{X}$ (atomic $\mathrm{wt}.$ $=125$ ) crystallises is simple cubic structure. If diameter of the largest atom which can be placed without disturbing unit cell is $366\mathrm{pm}.$ Find the density of pure element $\mathrm{X}$ in $\frac{\mathrm{gm}.}{{\mathrm{cm}}^3}$

$[$ Given : $\sqrt{3}=1.732,{ \mathrm{N}}_{\mathrm{A}}=6\times {10}^{23}]$

Which of the following statements is correct in the rock-salt structure of an ionic compound?

The coordination number of cation and anion in fluorite ${\mathrm{CaF}}_2$ and anti-fluorite ${\mathrm{Na}}_2\mathrm{O}$ are respectively:

In the closest packing of atoms A (radius = r), the radius of atom B that can be fitted into tetrahedral void is: