1.24. What type of substances would make better permanent magnets, ferromagnetic or ferrimagnetic. Justify your answer.
1.23 . A group 14 element is to be converted into n-type semiconductor by doping it with a suitable impurity. To which group should this impurity belong?
1.22. Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example.
1.21. Explain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it.
1.19. What type of defect can arise when a solid is heated? Which physical property is affected by it and in what way?
1.18. An element with molar mass forms a cubic unit cell with edge length . If its density is what is the nature of the cubic unit cell?
1.17 Which of the following lattices has the highest packing efficiency
(i) simple cubic
(ii) body-centred cubic and
(iii) hexagonal close-packed lattice?
1.16 A compound is formed by two elements and . The element forms ccp and atoms of occupy of tetrahedral voids. What is the formula of the compound?
1.15 A compound forms hexagonal close-packed structure. What is the total number of voids in of it? How many of these are tetrahedral voids?
Q. 1.13 Explain how much portion of an atom located at
(i) corner and
(ii) bodycentre of a cubic unit cell is part of its neighbouring unit cell.