Definitions [7]
Define the term ‘amorphous’.
The solids which do not possess the repeating ordered arrangement of atoms or ions are called amorphous solids.
Define Anisotropy.
The ability of crystalline solids to change values of physical properties when measured in different directions is called anisotropy.
Define unit cell.
A basic repeating structural unit of a crystalline solid is called a unit cell.
Definition: Extrinsic Semiconductor
A doped semiconductor, having higher conductivity than a pure intrinsic semiconductor, is an extrinsic semiconductor.
Definition: Intrinsic Semiconductor
A pure semiconductor with very low but finite electrical conductivity is called an intrinsic semiconductor.
Definition: Doping
The process by which impurities are introduced into semiconductors to enhance their conductivity is called doping.
Define the following term:
Ferromagnetism
Ferromagnetism is defined as the phenomenon in which substances, such as iron, cobalt and nickel, are strongly attracted by a magnetic field. Such substances are called ferromagnetic substances.
Theorems and Laws [1]
Name the law or principle to which the following observations confirm:
When 9650 coulombs of electricity is passed through a solution of copper sulphate, 3.175 g of copper is deposited on the cathode (at. wt. of Cu = 63.5).
Faraday’s first law of electrolysis: The mass of a substance deposited or liberated at an electrode is directly proportional to the quantity of electricity passed through the electrolyte.
Given: Charge passed = 9650 C
Atomic mass of Cu = 63.5
Valency of Cu in CuSO4 = 2
Equivalent mass of Cu = `63.5/2` = 31.75
Now, Mass deposited = `9650/96500 xx 31.75`
= 0.1 × 31.75
= 3.175 g
Key Points
Key Points: Classification of Crystalline Solids
| Property | Ionic Solids | Covalent Network Solids | Molecular Solids | Metallic Solids |
|---|---|---|---|---|
| Particles | Cations and anions | Covalently bonded atoms | Mono/polyatomic molecules | Metal ions in a sea of electrons |
| Forces | Electrostatic | Covalent bonds | London, dipole-dipole, H-bonding | Metallic bonds |
| Hardness | Hard and brittle | Very hard | Soft | Soft to very hard |
| Melting point | 600–3000°C | 1200–4000°C | Low (−272 to 400°C) | −39 to 3400°C |
| Conductivity | Poor (solid); good (molten/aqueous) | Poor (except graphite; diamond conducts heat) | Poor | Good conductor of heat and electricity |
| Examples | NaCl, CaF₂ | Diamond, silica | Ice, benzoic acid | Na, Mg, Cu, Au |
Key Points: Electrical Properties of Solids
Solids are classified into three groups based on conductivity:
| Type | Conductivity (Ohm⁻¹ m⁻¹) | Band Gap | Reason | Examples |
|---|---|---|---|---|
| Metallic conductors | 10⁴ – 10⁷ (very high) | No band gap (overlapping s & p bands) | Motion of electrons | Cu, Al, Ag |
| Insulators | 10⁻²⁰ – 10⁻¹⁰ (very low) | Large (forbidden zone) | Electrons cannot cross | Diamond, wood, rubber |
| Semiconductors | 10⁻⁶ – 10⁴ (moderate) | Small | Motion of interstitial electrons/holes | Si, Ge |
Conductivity of metals decreases with increase in temperature; conductivity of semiconductors increases with temperature.
Key Points: Magnetic Properties of Solids
Motion of electrons generates a magnetic field — each electron behaves like a tiny bar magnet with a magnetic moment measured in Bohr Magneton (μ_B) = 9.27 × 10⁻²⁴ A m².
| Type | Nature | Electron Configuration | Examples |
|---|---|---|---|
| Diamagnetic | Weakly repelled by magnetic field; magnetised in opposite direction | All electrons paired | NaCl, H₂O, N₂, C₆H₆, F₂, benzene |
| Paramagnetic | Weakly attracted by magnetic field; magnetised in same direction | Unpaired electrons; lose magnetism when field removed | O₂, Cu²⁺, Fe³⁺, Cr³⁺ |
| Ferromagnetic | Strongly attracted; can be permanently magnetised (all domains align in field direction) | Unpaired electrons + aligned domains | Fe, Co, Ni, Gd, CrO₂ |
Important Questions [53]
- Which of the following is not a characteristic of a crystalline solid?
- Based on the Nature of Intermolecular Forces, Classify the Following Solids: Sodium Sulphate, Hydrogen
- Write Any Two Differences Between Amorphous Solids and Crystalline Solids
- Account for the Following : O-nitrophenol is More Steam Volatile than P-nitrophenol.
- Give an Example Each of a Molecular Solid and an Ionic Solid.
- What is the covalency of nitrogen in N2O5?
- Define the Following Term: Primitive Unit Cells
- How will you distinguish between the following pair of terms? Crystal lattice and unit cell
- What is the formula of a compound in which the element Y forms ccp lattice and atoms of X occupy 1/3rd of tetrahedral voids?
- An element has atomic mass 93 g mol−1 and density 11.5 g cm–3. If the edge length of its unit cell is 300 pm, identify the type of unit cell. (NA = 6.023 × 1023 mol−1)
- How many atoms constitute one unit cell of a face-centered cubic crystal?
- An Element Crystallises in a B.C.C Lattice with Cell Edge of 500 Pm. the Density of the Element is 7.5g Cm-3. How Many Atoms Are Present in 300 G of the Element?
- An element with molar mass 27 g mol−1 forms a cubic unit cell with edge length 4.05 ✕ 10−8 cm. If its density is 2.7 g cm−3, what is the nature of the cubic unit cell?
- Calculate the Number of Unit Cells in 8.1 G of Aluminium If It Crystallizes in a F.C.C. Structure. (Atomic Mass of Al = 27 G Mol–1)
- An Element 'X' (At. Mass = 40 G Mol-1) Having F.C.C. the Structure Has Unit Cell Edge Length of 400 Pm. Calculate the Density of 'X' and the Number of Unit Cells in 4 G of 'X'. (Na = 6.022 × 1023 Mol-1)
- Formula of a compound in which the element Y forms hcp lattice and atoms of X occupy 2/3 of tetrahedral voids
- How will you distinguish between the following pair of terms? Tetrahedral and octahedral voids
- An Element Crystallises in Bcc Lattic with a Cell Edge of 3 × 10-8cm. the Density of the Element is 6.89 G Cm-3 . Calculate the
- An Element Crystallizes in Fcc Lattice with a Cell Edge of 300 Pm. the Density of the Element is 10.8 G Cm−3. Calculate the Number of Atoms in 108 G of the Element.
- Sum: An element with density 2.8 g cm–3 forms a f.c.c. unit cell with edge length 4 x 10–8 cm. Calculate the molar mass of the element.
- An element with density 10 g cm−3 forms a cubic unit cell with edge length of 3 × 10−8 cm. What is the nature of the cubic unit cell if the atomic mass of the element is 81 g mol−1?
- An element crystallizes in a f.c.c. lattice with cell edge of 250 pm. Calculate the density if 300 g of this element contain 2 × 10^24 atoms.
- An Element Crystallizes in Fcc Lattice with a Cell Edge of 300 Pm. the Density of the Element is 10.8 G Cm-3. Calculate the Number of Atoms in 108 G of the Element.
- An Element with Density 11.2 G Cm–3 Forms a F.C.C. Lattice with Edge Length of 4 × 10–8 Cm. Calculate the Atomic Mass of the Element. (Given : Na = 6.022 × 1023 Mol–1)
- What type of non-stoichiometric point defect is responsible for the pink colour of LiCl ?
- What Type of Stoichiometric Defect is Shown by Nacl ?
- What type of point defect is produced when AgCl is doped with CdCl2?
- Define the following term: Schottky defect
- Which Stoichiometric Defect Does Not Change the Density of the Crystal?
- Which Stoichiometric Defect Decreases the Density of the Crystal?
- What Type of Defect is Shown by Nacl in Stoichiometric Defects, and
- Out of Nacl and Agcl, Which One Shows Frenkel Defect and Why?
- Give Reasons : In Stoichiometric Defects, Nacl Exhibits Schottky Defect and Not Frenkel Defect.
- Answer the Following Question. What Type of Stoichiometric Defect is Shown by Zns and Why?
- Non-stoichiometric Defects?
- Examine the Given Defective Crystal:(I) What Type of Stoichiometric Defect is Shown by the Crystal? (Ii) How is the Density of the Crystal Affected by this Defect?
- What Happens When Cdcl2 is Doped with Agcl?
- The Cationic Vacancies Thus Produced Are Equal in Number to that of Cd2+ Ions. this is Impurity Defect.
- Account for the Following: Pcl5 is More Covalent than Pcl3.
- Account for the Following : Sncl4 is More Covalent than Sncl2.
- What Type of Semiconductor is Obtained When Ge is Doped with In?
- What Type of Semiconductor is Obtained When Si is Doped with P?
- What Type of Semiconductor is Obtained When Silicon is Doped with Boron?
- Give Reasons : Silicon on Doping with Phosphorous Forms N-type Semiconductor.
- Give Reasons:Ferrimagnetic Substances Show Better Magnetism than Antiferromagnetic Substances.
- What is ferromagnetism?
- Out of Cof63- and Co(En)33+, Which One Complex is (I) Paramagnetic (Ii) More Stable (Iii) Inner Orbital Complex and (Iv) High Spin Complex (Atomic No. of Co = 27)
- Write the Type of Magnetism Observed When the Magnetic Moments Are Aligned in Parallel and Anti-parallel Directions in Unequal Numbers.
- What type of magnetism is shown in the following alignment of magnetic moments? Ferromagnetism
- Give reason for the following : Sulphur in vapour state shows paramagnetic behaviour.
- Write the Type of Magnetism Observed When the Magnetic Moments Are Oppositely Aligned and Cancel Out Each Other.
- Define the following term: Ferromagnetism
- What Type of Magnetism is Shown by a Substance If Magnetic Moments of Domains Are Arranged in Same Direction?
Concepts [23]
- General Characteristics of Solid State
- Amorphous and Crystalline Solids
- Classification of Crystalline Solids
- Crystal Lattices and Unit Cells
- Crystal Lattices and Unit Cells - Primitive and Centred Unit Cells
- Number of Atoms in a Unit Cell
- Close Packed Structures of Solids
- Close Packed Structures - Formula of a Compound and Number of Voids Filled
- Packing Efficiency in hcp and ccp Structures
- Efficiency of Packing in Body-centred Cubic Structures
- Packing Efficiency in Simple Cubic Lattice
- Calculations Involving Unit Cell Dimensions
- Imperfections in Solids - Introduction
- Types of Point Defects - Stoichiometric Defects
- Types of Point Defects - Impurity Defects
- Types of Point Defects - Non-stoichiometric Defects
- Properties of Solids: Electrical Properties
- Conduction of Electricity in Metals
- Conduction of Electricity in Semiconductors
- Applications of n-type and p-type Semiconductors
- Properties of Solids: Magnetic Properties
- Band Theory of Metals
- Solid State Numericals
