i. Calculate the packing efficiency and density of NaCl from following data Radius of Sodium ion 0.98 The unit cell dimension of bce iron is 2.81 x 10 10 m. Find metallic radius of iron atom. ii. Radius of Sodium ion = 1.81 %3D Atomic mass of sodium = 22.99 amu Atomic mass of chlorine 35.45 amu iii. Prove that in determining lattice parameters, the greater the diffraction angle the greater the accuracy iv. Calculate Bragg angle at which electrons accelerated from rest through a potential difference of 8oV will be diffracted from (111) planes of an fcc lattice of crystal parameter 3.5 .