Sodium metal crystallizes in a body centred cubic lattice with unit cell edge of $4.29 {\mathrm{A}}^{°}$ . The radius of sodium atom is approximately

If the unit cell of mineral has cubic close packed (ccp) array oxygen atoms with $\mathrm{m}$ fraction of octahedral holes occupied by aluminium ions and $\mathrm{n}$ fraction of tetrahedral holes occupied by magnesium ions, $\mathrm{m}$ and $\mathrm{n}$, respectively, are

Lithium has a bcc structure. Its density is $530 \mathrm{kg} {\mathrm{m}}^{-3}$ and its atomic mass is $6.94 \mathrm{g} {\mathrm{mol}}^{-1}$. Calculate the edge length of a unit cell of lithium metal.

A metal crystallises in a face-centred cubic structure. If the edge length of its unit call is '$\mathrm{a}$', the closest approach between two atoms in metallic crystal will be

Iron exhibits bcc structure at room temperature. Above $900 °\mathrm{C}$, it transforms to fcc structure. The ratio of density of iron at room temperature to that at $900 °\mathrm{C}$ (assuming molar mass and atomic radii of iron remains constant with temperature) is