2Na⁺ will replaced by Mg²⁺ ion to maintain electrical neutrality thus ahole created for lattice site for every Mg²⁺ ion introduce thus the defect produced will schottky defect

When ferromagnetic substance is subjected to high temperature it loses its magnetic property and become paramagnetic in nature this happen due to disorder ness in electronic arrangment.

arsenic (As) or phosphorus (P).

Body centre wholly belongs to the unit cell in which it is present. Thus
in a body-centered cubic (bcc) unit cell:
(i) 8 corners × 1/8per corner atom= 8 x 1/8 = 1 atom
(ii) 1 body centre atom = 1 × 1 = 1 atom
∴ Total number of atoms per unit cell = 2 atoms
For face centred 

(i) 8 corners atoms × 1/8 atom per unit cell
= 8  x1/8 = 1 atom

(ii) 6 face-centred atoms ×1/2 atom per unit cell = 6 ×1/2 = 3 atoms
∴ Total number of atoms per unit cell = 4 atoms

The maximum possible coordination number of an atom in hcp structure of an element is 12.