Solid State – An Introduction
Introduction:
In the world of physics and chemistry, Solid State is an important subject that deals with the properties and internal structure of substances in the solid phase. It is widely used in technologies like electronics, material science, computer hardware, and nanotechnology.
What is Solid State?
Solid state refers to the phase in which the particles (atoms, ions, or molecules) of a substance are closely packed in a regular structure. In this state, the substance has a definite shape and volume.
Characteristics of Solid State:
- Definite shape and volume – Solids have a fixed shape and volume.
- Close packing of particles – Particles are very close and can only vibrate.
- High density and hardness – Solids are generally denser and harder than liquids and gases.
- Low solubility – Most solids do not easily dissolve in liquids.
Types of Solids:
Crystalline Solids:
These have particles arranged in a definite geometric structure. Examples – Salt (NaCl), Diamond. These are further classified into:
- Ionic solids
- Molecular solids
- Metallic solids
- Network solids
Amorphous Solids:
These lack a definite arrangement of particles. Examples – Glass, Plastic.
Importance of Solid State:
The study of solid state is the foundation of modern technological advancement. Solid-state electronics like semiconductors, transistors, diodes, and computer chips are based on this principle. From smartphones to artificial intelligence (AI), solid state plays a vital role in every technology.
Conclusion:
Solid state is not just a physical phase, but also the backbone of modern science and technology. A deep understanding of it helps in mastering physics and chemistry, and guides the development of new technologies.
Solid State – 50 MCQs with Options
1. Which type of solid has long-range order?
A. Crystalline solid B. Amorphous solid C. Gas D. Liquid
2. In an NaCl crystal, each Na⁺ ion is surrounded by how many Cl⁻ ions?
A. 4 B. 6 C. 8 D. 2
3. Which type of solids do not conduct electricity?
A. Metallic B. Ionic (in solid state) C. Semiconductor D. Superconductor
4. What force binds particles in ionic solids?
A. Van der Waals forces B. Electrostatic forces C. Metallic bonds D. Hydrogen bonds
5. Graphite is an example of which solid?
A. Ionic B. Metallic C. Molecular D. Network solid
6. How many atoms are there in one FCC unit cell?
A. 2 B. 4 C. 6 D. 8
7. What makes diamond so hard?
A. Ionic bond B. Network structure C. Metallic bond D. Van der Waals forces
8. What is a feature of amorphous solids?
A. Definite melting point B. Irregular structure C. Long-range order D. Crystal structure
9. Which solid is used as a semiconductor?
A. NaCl B. Si C. CCl₄ D. MgO
10. What is used to dope pure silicon to make it a semiconductor?
A. Na B. B C. Cl D. O₂
11. An example of a cation vacancy is:
A. Excess of electrons in metal B. Cation vacancy C. Anion vacancy D. Excess of cations
12. What is the basic unit of a crystal?
A. Unit cell B. Atom C. Ion D. Molecule
13. Lack of chloride ion indicates which defect?
A. Schottky B. Frenkel C. Metallic D. Electronic
14. Which solids are soft and have low melting points?
A. Ionic B. Molecular C. Metallic D. Network
15. How many atoms are present in one BCC unit cell?
A. 1 B. 2 C. 3 D. 4
(Next 35 questions are listed below.)
16. What increases conductivity in semiconductors?
17. What type of bond exists in metallic solids?
18. What dopant is present in 'n-type' semiconductors?
19. What type of crystal is NaCl?
20. In which state do ionic solids conduct electricity?
21. Which unit cell has the highest density?
22. What type of defect is found in ZnS?
23. What are vacancies in crystals called?
24. How many faces are there in an FCC unit cell?
25. How many atoms are at the body center in BCC?
26. What is the structure of SiO₂?
27. What type of solid is ice?
28. Molecular solids are composed of?
29. What are examples of amorphous solids?
30. What happens to the conductivity of semiconductors on heating?
31. Which crystal conducts electricity without ions?
32. What is a feature of metallic solids?
33. What color does ZnO turn when heated?
34. Which structure has the highest packing efficiency?
35. What is the geometric shape of a crystal called?
36. Which is a non-conducting solid?
37. What percentage of space is occupied by a tetrahedral void?
38. In which defect does an ion move to an interstitial position?
39. Electronic defect is related to what?
40. What type of crystal is MgO?
41. What is the packing efficiency of FCC structure?
42. In which solid are molecules held only by van der Waals forces?
43. What is an example of Schottky defect?
44. Where are semiconductors used?
45. What are the defects in solid crystals called?
46. Which solid is brittle?
47. Which solid has a hexagonal structure?
48. What is the crystal structure of CaF₂?
49. Silicon dioxide is a:
50. How many equal edges are there in a tetragonal unit cell?
Answers to 50 MCQs (in order):
- A. Crystalline solid
- B. 6
- B. Ionic (solid state)
- B. Electrostatic forces
- D. Network solid
- B. 4
- B. Network structure
- B. Irregular structure
- B. Si
- B. B
- B. Cation vacancy
- A. Unit cell
- D. Electronic
- B. Molecular
- B. 2
- By doping (adding dopants)
- Metallic bond
- Group 15 elements (e.g., P, As)
- Ionic crystal
- In molten or dissolved state
- FCC
- Frenkel defect
- Vacancy
- 6
- 1
- Network solid
- Molecular solid
- Molecules
- Glass, Plastic
- Conductivity increases
- Metals
- High conductivity, ductility
- Yellow
- FCC or HCP
- Crystal lattice
- Molecular solid
- Around 0.225 (22.5%)
- Frenkel defect
- Excess/deficiency of electrons
- Ionic solid
- 74%
- Molecular solid
- NaCl
- Transistors, Diodes
- Point defects
- Ionic solid
- Zn
- Fluorite structure
- Network solid
- Two