Give reasons :
(i) In stoichiometric dfects. NaCl exhibits Schottky defect and not Frenkel defect.
(iii) Ferrimagnetic substances show better magnetism than antiferromagnetic substances.

Explanation

(i)Schottky defect is shown by those ionic compounds which have small difference in the size of cation and anion whereas Frenkel defect is shown by those compounds which have large differences in the size of cation and anion. As the difference in the size of `Na^+` and `Cl^-` ions is small, hence it shows Schottky defect. (ii)Silicon belongs to Group 14 whereas phosphorus belongs to Group 15. As phosphorus has one extra electron than silicon, this extra electron makes silicon a semiconductor. Hence , we get n-type semiconductor.
(iii)Ferrimagnetic substances have an unequal number of electrons with spin in the opposite direction. with spin in the opposite direction. Hence, their net magnetic moment is zero. For this reason, ferrimagnetic substances show better magnetism than antiferromagnetic substances .