CBSE Question Bank on
THE SOLID STATE
1. An element occurs in bcc structure. How many atoms are present in its unit cell? 
2. What causes the conduction of electricity by semiconductors ? [SP 1997]
3. A cubic solid is made of two elements P and Q. Atoms Q are at corners of the cube
and P at the body-centre. What is the formula of the compound ? What are the
coordination numbers of P and Q ? [1997D]
4. Copper crystallizes in face-centered cubic lattice and has a density of 8.930 g/cm3 at
293 K. Calculate the radius of copper atom. (At. mass of Cu = 63.55 u) [1997D]
5. An element occurs in bcc structure. It has a cell edge length of 250 pm. Calculate its
molar mass if its density is 8.0 g/cm3 .
6. Metallic gold crystallises in a fcc lattice and has a density of 19.3 g/cm3 . Calculate
the radius of gold atom. (At. mass of gold = 197 u)
7. What are non-stoichiometric compounds ? [1998AI]
8. What may be the difference between Phosphorus doped and Gallium doped
semiconductors ? [1998F]
9. Why is Frenkel defect found in AgCl ? [1999AI]
10. Name the two types of crysal imperfections. [1999AI]
11. Why does a pure silicon which is an insulator, behave as a semiconductor on
heating ? [1999D]
12. How many atoms are there in a unit cell of a metal crystallizing in fcc structure? 
13. An element A crystallises in fcc structure, 208 g of this element has 4.283 × 1024 atoms.
If edge length of the unit cell of this element is 408 pm, calculate its density. [1999AI]
14. An element crystallizes in fcc structure. Its density is 7.9 g/cm3 . 208 g of this element
has 4.283 × 1024 atoms. Calculate the edge length of the unit cell. [1999D]
15. Which point defect lowers the density of ionic crystals ? [2000AI]
16. Determine the type of cubic lattices to which the iron crystal belongs if its cell has an
edge length of 268 pm and the density of iron crystal is 7.86 g/cm3 .
(At. weight of Fe = 56 g/mol)
17. An element exists in bcc structure with a cell edge of 288 pm. If the density of the
element is 7.2 g/cm3 , what is atomic mass of the element ? [2000AI&F]
18. What is the difference between ferromagnetic and ferrimagnetic substances ? [2001D]
19. Why does Frenkel defect not change the density of AgCl crystal ? [2001AI]
20. What other elements may be added to silicon to make electrons available for the
conduction of electric current ?
21. An element A crystallizes in fcc structure. 200 g of this element has 4.12 × 1024
atoms. The density of A is 7.2 g/cm3 . Calculate edge length of unit cell. [2001AI]
22. Sodium crystallizes in the cubic lattice and the edge length of the unit cell is 430 pm.
Calculate the number of atoms in a unit cell.
(At. mass of Na = 23.0 and density = 0.9623 g/cm3 )
23. Lithium metal crystal has body centered cubic structure. Its density is 0.53 g/cm3
and its molar mass is 6.94 g/mol. Calculate the volume of unit cell of lithium
24. If NaCl crystals are doped with 2 × 10-3 mol per cent of SrCl2, calculate the cation
vacancies per mole.
25. Unit cell of an element (atomic mass 108 u and density 10.5 g/cm3 ) has an edge
length 409 pm. Deduce the type of crystal lattice.
26. An element having bcc structure has atomic mass 50 u and density 6.81 g/cm3 .
Calculate the edge length of the unit cell.
27. State the difference between Schottky and Frenkel defects. Which of the two changes
the density of the solid ?
28. Mention one property which is caused due to the presence of F-centre in a solid.
29. Which solid is likely to be the best material for converting sunlight into electricity ?
30. In an alloy of gold and cadmium, gold crystallizes in cubic structure occupying the
corners only and cadmium fits into the face centre voids. What is quantitative
composition of the alloy ?
31. What is the difference between glass and quartz, through both contain SiO44- units ?
32. Name on solid in which both Frenkel and Schottky defects occur. [2003AI]
33. What is the effect of Frenkel defect on electrical conductivity of the solid ? [2003AI]
34. An element occurs in bcc structure with cell edge 300 pm. The density of the element
is 5.2 g/cm3 . How many atoms of the element does 200 g of the element contain ?
35. The density of chromium ion metal is 7.2 g/cm3. If the unit cell has edge length of
289 pm, determine the type of unit cell. (At. mass of Cr = 52 u)
36. Name a substance which on addition to AgCl causes cation vacancy in it. [2004D]
37. What makes alkali metal halides sometimes coloured, which are otherwise colourless ?
38. Define the term ‘amorphous’.
39. Which point defect lowers the density of a crystal ?
40. What is coordination number of a metal atom in ccp structure ?
41. Why is common salt sometime yellow instead of being pure white ? [2004 F]
42. Why are Frenkel defects not found in pure alkali halides ? [2004D]
43. What happens when ferrimagnetic Fe3O4 is heated at 850 K and why ? [2004AI]
44. How can a ferromagnetic substance be changed to paramagnetic one ? [2004AI]
45. What is the nature of crystal defect produced when sodium chloride is doped with
46. Name an element with which germanium can be doped to produce an n-type
47. What happens when a ferromagnetic substance is subjected to high temperature ?
48. Why is potassium chloride sometimes violet instead of pure white ? [2005AI]
49. How many atoms can be assigned to its unit cell if an element forms (i) a body
centred cubic cell and (ii) a face centred cubic cell ? [2005AI]
50. What is the maximum possible coordination number of an atom in an hcp crystal
structure of an element ?
51. Aluminium crystallizes in a cubic closed-packed structure. Its metallic radius is 125 pm
(a) What is the length of the side of the unit cell ?
(b) How many unit cells are there in 100 cm3 of aluminium ?
52. (a) Determine the type of cubic lattice to which a given crystal belongs if it has edge
length of 290 pm and density is 7.80 g/cm3
(molecular mass = 56 g/mol)
(b) Why does zinc oxide exhibit enhanced electrical conductivity heating ? [2005D]
53. What is the effect of Schottky a Frenkel defects on the density of crystalline solids ?
54. A cubic solid is made of two elements X and Y. Atoms Y are at the corners of the
cube and X at the body centre. What is the formula of the compound ? [2006D]
55. Name the non-stoichiometric point defect responsible for colour in alkali halides.
56. Name an element with which silicon can be doped to give a p-type semiconductor.
57. Name the crystal defect which lowers the density of an ionic crystal. [2006D]
58. What makes the crystal of KCl appear sometime violet ? [2006AI]
59. Copper is conducting as such while sulphate is conducting only in molten state or
in aqueous solution. Give reasons.
60. Explain n type semiconductors with examples.
61. (a) With reference to crystal structure, what is meant by coordination number ?
(b) What is the coordination number of atoms
(i) in a cubic close packed structure.
(ii) in a body-centred cubic structure ?
62. What is semiconductor ? Describe two main types of semiconductors giving examples
and their distinctive features.
63. Calculate the efficiency of packing in case of a metal crystal for simple cubic. [2006AI]
64. What is the coordination number of a rock salt type structure. [2007F]
65. Name an element with which silicon can be doped to give n-type semiconductors.
66. Explain with suitable examples : (i) Paramagnetism
(ii) Frenkel defect in crystals
67. Assign reasons for the following :
(i) Phosphorus doped silicon is semiconductor.
(ii) Schottky defect lowers the density of a solid.
(iii) Some of very old glass objects appears slightly milky instead of being pure
68. What type of substances exhibits antiferromagnetism ?
69. How would you account for the following ?
(i) Frenkel defects are not found in alkali metal halides.
(ii) Impurity doped silicon is a semiconductor.
70. Explain the following properties giving suitable examples :
71. Silver crystallizes in an fcc lattice. The edge length of a unit cell is 4.077 × 10-8 cm.
And its density is10.5 g/cm3. Calculate the atomic mass of silver. [2008AI]
72. What type of alignment in crystals make them ferromagnetic ? [2008F]
73. Explain with suitable examples : Frenkel defect and F-centres.
74. Iron has body centred cubic unit cell with a cell edge of 286.65 pm. The density of iron
Is 7.87 g/cm3 . Use this information to calculate Avogadro number.
(Atomic weight of Fe = 56 g/mol)
75. Silver crystallizes with face-centred cubic unit cells. Each side of the unit cell has a
Length of 409 pm. What is the radius of an atom of silver ?