Properties and Types of Solids
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Questions and Answers

What is the state of matter where constituents are firmly bound due to strong forces?

solid

What are the two types of solids that are classified based on their constituent arrangement?

crystalline and amorphous

What is the defining characteristic of crystalline solids regarding constituent arrangement?

Constituents are arranged in a definite or proper order which repeats itself.

Crystalline solids are isotropic.

<p>False (B)</p> Signup and view all the answers

What is the defining characteristic of amorphous solids regarding constituent arrangement?

<p>Constituents are not arranged in a regular or orderly manner.</p> Signup and view all the answers

What is the term used to describe the homogeneous part of a solid substance formed by a regular pattern of structural units?

<p>Crystal</p> Signup and view all the answers

What is the name for the regular arrangement of constituent particles (atoms, ions, etc.) of a crystal in 3-D space?

<p>Crystal lattice or space lattice</p> Signup and view all the answers

What is the angle between the perpendiculars of two intersecting faces called?

<p>Interfacial angle</p> Signup and view all the answers

What is the reason behind the thicker bottom of glass panes in old buildings?

<p>Due to the fluidity of glass as a supercooled liquid, it flows over time, resulting in a thicker bottom.</p> Signup and view all the answers

What is the reason behind the milky appearance of old glass?

<p>Due to annealing over time, glass obtains some crystalline character.</p> Signup and view all the answers

Which type of crystalline solid has high melting points and is a good conductor of electricity?

<p>Metallic (C)</p> Signup and view all the answers

What is the angle formed when three or more than three edges intersect?

<p>Solid angle</p> Signup and view all the answers

What is the equation that relates the wavelength of X-rays, the distance between crystal planes, and the angle of reflection?

<p>Bragg's equation: ηλ = 2d sin θ</p> Signup and view all the answers

What is the reason behind the electrical conductivity of metallic solids?

<p>Due to their bonding, metallic solids have delocalized electrons, which are free to move and conduct electricity.</p> Signup and view all the answers

What is the smallest three-dimensional portion of a space lattice that, when repeated in different directions, creates the complete lattice?

<p>Unit cell</p> Signup and view all the answers

What is the shape of the unit cell in the NaCl crystal structure?

<p>Cube</p> Signup and view all the answers

What is the coordination number of atoms at the corners of a simple cubic unit cell?

<p>8</p> Signup and view all the answers

What is the coordination number of atoms at the face centers of a face-centered cubic unit cell?

<p>12</p> Signup and view all the answers

What is the coordination number of atoms at the body center of a body-centered cubic unit cell?

<p>8</p> Signup and view all the answers

In a crystal structure, how is the symmetry represented?

<p>A crystal may possess centre of symmetry, axis of symmetry, and plane of symmetry.</p> Signup and view all the answers

What is the symmetry of a sphere?

<p>A sphere has all types of symmetry: point, axis, and plane.</p> Signup and view all the answers

What are the seven crystal systems?

<p>Cubic, Orthorhombic, Tetragonal, Monoclinic, Triclinic, Hexagonal, Rhombohedral.</p> Signup and view all the answers

What is a rectangular plane of symmetry?

<p>It is an imaginary plane that divides a crystal into two equal parts, creating mirror images of each other.</p> Signup and view all the answers

What is a diagonal plane of symmetry?

<p>It is an imaginary plane that divides a crystal into two equal parts, creating mirror images of each other by passing through the center of the crystal and intersecting opposite faces.</p> Signup and view all the answers

What is an axis of four-fold symmetry?

<p>It is an imaginary line through the center of a crystal where rotation by 90 degrees produces the same appearance.</p> Signup and view all the answers

What is the center of symmetry?

<p>It is an imaginary point at the center of a crystal where any line through it passes through two equidistant points on the surface of the crystal.</p> Signup and view all the answers

What is the definition of atomic radius in a crystal structure?

<p>Half the distance between two nearest neighboring atoms in the crystal.</p> Signup and view all the answers

What is the formula for calculating the atomic radius (r) in a simple cubic unit cell?

<p>The formula for the atomic radius (r) in a simple cubic cell is r = a/2, where a is the edge length of the unit cell.</p> Signup and view all the answers

Match the types of cubic unit cells with their corresponding formula for the atomic radius (r) based on the edge length (a).

<p>Simple cubic = r = a/2 Face-centered cubic (FCC) = r = √2a/4 Body-centred cubic (BCC) = r= √3a/4</p> Signup and view all the answers

What is the term used to describe the ratio of the volume occupied by spheres in a unit cell to the total volume of the unit cell?

<p>Packing fraction</p> Signup and view all the answers

What is the formula for calculating the packing fraction in a simple cubic unit cell?

<p>The formula for calculating the packing fraction in a simple cubic unit cell is PF = πr³/6a³, where r is atomic radius and a is the edge length of the unit cell.</p> Signup and view all the answers

What is the formula for calculating the packing fraction in a face-centered cubic unit cell?

<p>The formula for calculating the packing fraction in a face-centered cubic unit cell is PF = 4πr³/3a³, where r is atomic radius and a is the edge length of the unit cell.</p> Signup and view all the answers

What are the empty spaces between close-packed spheres called?

<p>Interstitial voids</p> Signup and view all the answers

What are the three types of interstitial voids?

<p>Trigonal, tetrahedral, and octahedral voids</p> Signup and view all the answers

Which interstitial void is formed by combination of two triangular voids?

<p>Octahedral void (A)</p> Signup and view all the answers

What is the coordination number for tetrahedral void?

<p>4</p> Signup and view all the answers

What is the formula for calculating the volume of a tetrahedral void?

<p>Vtetrahedral = 0.214 x r</p> Signup and view all the answers

What is the ratio of the radius of an octahedral void to the radius of the sphere forming the close-packed arrangement?

<p>Radius ratio</p> Signup and view all the answers

What is the maximum number of oppositely charged ions surrounding a given ion in a crystal structure called?

<p>Coordination number</p> Signup and view all the answers

What is the formula for calculating the radius ratio in a crystal structure?

<p>Radius ratio = Radius of cation / Radius of anion</p> Signup and view all the answers

What is the definition of close packing in two dimensions?

<p>An arrangement where each sphere is in contact with four other spheres.</p> Signup and view all the answers

How much space is occupied by spheres in square close packing?

<p>About 52.4%</p> Signup and view all the answers

What is the defining characteristic of hexagonal close packing?

<p>Each sphere is in contact with six other spheres.</p> Signup and view all the answers

How much space is occupied by spheres in hexagonal close packing?

<p>About 60.4%</p> Signup and view all the answers

What are the three types of close packing in three dimensions?

<p>Hexagonal close packing, cubic close packing, and body-centered cubic packing</p> Signup and view all the answers

What is the coordination number for spheres in cubic close packing?

<p>12</p> Signup and view all the answers

What is the coordination number for spheres in hexagonal close packing?

<p>12</p> Signup and view all the answers

What is the coordination number for spheres in body-centered cubic packing?

<p>8</p> Signup and view all the answers

What is the general formula for spinel structure?

<p>AB₂O₄</p> Signup and view all the answers

What are the two types of spinel structures?

<p>Normal spinel and inverse spinel</p> Signup and view all the answers

What is the reason for imperfections in crystals?

<p>Defects are deviations from perfectly ordered arrangement in crystalline structures.</p> Signup and view all the answers

Why are defects also known as thermodynamic defects in crystals?

<p>The number of defects in a crystal is dependent on temperature.</p> Signup and view all the answers

What are the two main types of stoichiometric defects?

<p>Schottky and Frenkel defects</p> Signup and view all the answers

What is the mechanism behind Schottky defects?

<p>Missing pairs of cations and anions from their respective lattice positions, creating vacancies.</p> Signup and view all the answers

What is the mechanism behind Frenkel defects?

<p>An ion leaving its lattice site and occupying an interstitial site, creating a vacancy and an interstitial ion.</p> Signup and view all the answers

In a non-stoichiometric crystal, what is the reason for an excess of metal ions compared to the stoichiometric ratio?

<p>It occurs when the crystal contains an excess of metal ions due to the presence of vacancies in the lattice.</p> Signup and view all the answers

What is the term for the presence of metal ions in interstitial sites in a crystal structure?

<p>Metal excess defect</p> Signup and view all the answers

What is the term for the presence of vacancies in a crystal structure due to missing metal ions?

<p>Metal deficiency defect</p> Signup and view all the answers

What type of material exhibits diamagnetism?

<p>Diamagnetic materials have all paired electrons, meaning they have no unpaired electrons.</p> Signup and view all the answers

What is the temperature at which a ferromagnetic material changes its magnetic properties and loses its ferromagnetic behavior?

<p>Curie temperature</p> Signup and view all the answers

What is the defining characteristic of antiferromagnetic materials?

<p>Antiferromagnetic materials have unpaired electrons that align in opposite directions, resulting in a net magnetic moment of zero.</p> Signup and view all the answers

What is the process of doping semiconductor materials with impurities to enhance their conductivity called?

<p>Doping</p> Signup and view all the answers

What is the phenomenon observed when a mechanical force is applied on a polar crystal, resulting in the generation of electricity?

<p>Piezoelectricity</p> Signup and view all the answers

What is the phenomenon observed when a polar crystal is heated, resulting in the generation of electricity?

<p>Pyroelectricity</p> Signup and view all the answers

What is the phenomenon observed when a polar crystal exhibits permanent polarization even in the absence of an electric field, and its polarization direction can be altered by applying an electric field?

<p>Ferroelectricity</p> Signup and view all the answers

What is the definition of antiferroelectricity?

<p>Antiferroelectricity occurs when electric dipoles in a crystal arrange in opposite directions, resulting in no net dipole moment.</p> Signup and view all the answers

What is superconductivity?

<p>Superconductivity is defined as the absence of resistance to the flow of electricity at a specific temperature.</p> Signup and view all the answers

What are the major applications of superconductors?

<p>Superconductors find applications in areas like building super magnets, electronic power transmission, and other advanced technologies.</p> Signup and view all the answers

What are the substances that exhibit electrical conductivity in the range of 10⁴-10⁷ Ω-¹ cms at room temperature?

<p>Semiconductors</p> Signup and view all the answers

What are the semiconductors that exhibit conductivity due to impurities?

<p>Extrinsic semiconductors</p> Signup and view all the answers

What are the semiconductors that exhibit intrinsic conductivity?

<p>Intrinsic semiconductors</p> Signup and view all the answers

What is the process of adding impurities into intrinsic semiconductors to modify their conductivity called?

<p>Doping</p> Signup and view all the answers

What type of semiconductor is formed when elements like phosphorus or arsenic are doped into silicon?

<p>n-type semiconductor</p> Signup and view all the answers

What type of semiconductor is formed when elements in group 3 (e.g., gallium) are doped into silicon?

<p>p-type semiconductor</p> Signup and view all the answers

How are stoichiometric defects also called intrinsic defects?

<p>Stoichiometric defects are called intrinsic defects because they arise from the inherent properties of the crystal structure and do not involve external impurities.</p> Signup and view all the answers

What happens when CaCl₂ is added to an AgCl crystal?

<p>CaCl₂ introduces Schottky defects in the AgCl crystal.</p> Signup and view all the answers

How is electrical neutrality maintained in compounds exhibiting Schottky and Frenkel defects?

<p>Electrical neutrality is maintained in both cases due to the balanced removal of cations and anions in Schottky defects or the displacement of ions within the lattice in Frenkel defects.</p> Signup and view all the answers

Why does the electrical conductivity of metals decrease with an increase in temperature?

<p>With increasing temperature, the vibration of metal ions increases, obstructing the flow of electrons.</p> Signup and view all the answers

Why does the electrical conductivity of semiconductors increase with an increase in temperature?

<p>With increasing temperature, more electrons have sufficient energy to jump from the valence band to the conduction band.</p> Signup and view all the answers

What type of material is better suited for making permanent magnets: ferromagnetic or ferromagnetic?

<p>Ferromagnetic materials are better suited for making permanent magnets.</p> Signup and view all the answers

What are the different ways atoms A and B are arranged in a crystalline solid?

<p>Atoms A are arranged in a close-packed cubic array, while atoms B occupy all octahedral voids and half of the tetrahedral voids.</p> Signup and view all the answers

What is the coordination number for atoms arranged in a close-packed cubic array?

<p>12</p> Signup and view all the answers

How many octahedral voids are present in a close-packed cubic array?

<p>8</p> Signup and view all the answers

How many atoms are present at the corners of a cubic unit cell?

<p>8</p> Signup and view all the answers

How many atoms are present at the face centers of a cubic unit cell?

<p>6</p> Signup and view all the answers

If two corner atoms are missing from a cubic unit cell, what is the total number of atoms contributed from the corners?

<p>3</p> Signup and view all the answers

What is the total number of atoms in a cubic unit cell having one atom at each corner and two atoms on each body diagonal?

<p>9</p> Signup and view all the answers

What is the formula of a compound where Y atoms form a cubic close packed structure and X forms occupies 2/3rd of the tetrahedral voids?

<p>X₄Y₃</p> Signup and view all the answers

How many unit cells are present in 2 grams of potassium, which crystallizes in a body centered cubic lattice?

<p>1.54 x 10²² unit cells</p> Signup and view all the answers

What is the ideal radius of the cation in a crystal structure with NaCl-type close packing if the anion has a radius of 241.5 pm?

<p>100 pm</p> Signup and view all the answers

Can a cation with a radius of 50 pm fit into the tetrahedral void of a crystal with an NaCl-type structure if the anion has a radius of 241.5 pm?

<p>Yes</p> Signup and view all the answers

Flashcards

What is the difference between crystalline and amorphous solids?

Crystalline solids have a regular, repeating arrangement of atoms or molecules, resulting in a well-defined structure and sharp melting point. Amorphous solids lack a long-range order and have a more disordered arrangement, leading to a gradual softening over a range of temperatures.

What are the three phases of matter?

The three phases of matter are solid, liquid, and gas. Solids have a fixed shape and volume, liquids take the shape of their container but have a fixed volume, and gases have no fixed shape or volume and fill their container completely.

What is a unit cell?

The smallest repeating unit in a crystal lattice that represents the entire structure of the crystal. It's like a building block that, when repeated, creates the whole building.

What are the types of unit cells?

There are four types of unit cells: simple, face-centred, body-centred, and end-centred. Simple has atoms only at corners, face-centred has atoms at corners and face centres, body-centred has atoms at corners and the centre, and end-centred has atoms at corners and centres of two opposite faces.

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What is a point defect?

Deviations from the perfect arrangement of atoms or ions in a crystal lattice, affecting the physical properties of the solid.

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What is a Schottky defect?

A type of point defect where an equal number of cations and anions are missing from their lattice sites, creating a pair of vacancies. This defect occurs in ionic compounds with high coordination numbers and similar sizes of ions.

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What is a Frenkel defect?

A type of point defect where an ion leaves its regular lattice site and occupies an interstitial site, maintaining electrical neutrality. This defect is common in ionic compounds with low coordination numbers and significant size difference between ions.

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What are F-centres?

Vacancies in the crystal lattice occupied by electrons, leading to colour in the compound. These defects are usually associated with metal excess defects.

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How are electrical properties of solids classified?

Solids are classified as conductors, semiconductors, or insulators based on their electrical conductivity. Conductors have high conductivity due to free electrons, semiconductors have moderate conductivity, and insulators have very low conductivity.

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What are n-type semiconductors?

Semiconductors formed by doping a pure element (e.g., silicon) with a group 5 element (e.g., phosphorus), having an extra electron that can move freely and contribute to conductivity.

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What are p-type semiconductors?

Semiconductors formed by doping a pure element (e.g., silicon) with a group 3 element (e.g., gallium), creating 'holes' that act as positive charge carriers and contribute to conductivity.

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What is a ferromagnetic substance?

Substances that exhibit strong magnetism even in the absence of an external magnetic field. These materials have domains where magnetic moments are aligned in the same direction.

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What is an antiferromagnetic substance?

Substances with equal numbers of parallel and anti-parallel spins, resulting in a zero net magnetic moment. Examples include MnO, MnO2, FeO.

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What is a ferrimagnetic substance?

Substances with unequal numbers of parallel and anti-parallel spins, leading to a net magnetic moment. Examples include Fe3O4 (magnetite) and ferrites.

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What is piezoelectricity?

The generation of electricity in certain crystalline materials when subjected to mechanical stress. These crystals act as transducers, converting mechanical energy into electrical energy.

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What is pyroelectricity?

The generation of electricity in certain polar crystals when they are heated. This is due to temperature-induced changes in the dipole moments of the crystal.

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What is ferroelectricity?

A phenomenon in certain piezoelectric crystals where the dipoles are permanently polarized even without an electric field. Their polarization can be reversed by applying an external electric field.

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What is antiferroelectricity?

A phenomenon in some crystals where the dipoles align in an alternating up-and-down manner, resulting in zero net dipole moment.

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What is superconductivity?

The complete absence of electrical resistance in certain materials below a critical temperature. Superconductors can conduct electricity without any energy loss.

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What is doping in semiconductors?

The process of intentionally adding impurities to a pure semiconductor material to modify its conductivity. It can create either n-type or p-type semiconductors.

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What is coordination number in a crystal?

The number of nearest neighbor atoms or ions surrounding a central atom or ion in a crystal lattice. It indicates how closely packed the atoms are.

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What is radius ratio?

The ratio of the radius of a cation to the radius of an anion in an ionic compound. It helps predict the coordination number and structure of the crystal.

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How does a Schottky defect affect the density and electrical conductivity of a crystal?

A Schottky defect decreases the density of a crystal because some atoms are missing. It also increases electrical conductivity to a small extent due to the movement of ions to fill the vacancies.

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How does a Frenkel defect affect the density and dielectric constant of a crystal?

A Frenkel defect does not change the density but increases the dielectric constant of the crystal. The dielectric constant is a measure of how well a material can store electrical energy.

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What is the difference between stoichiometric and non-stoichiometric defects?

Stoichiometric defects do not change the ratio of cations to anions in a compound, while non-stoichiometric defects lead to a deviation from the ideal formula. Stoichiometric defects typically involve vacancies, while non-stoichiometric defects can involve either vacancies or interstitial atoms or ions.

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How do metal excess defects occur in a crystal?

Metal excess defects occur when a crystal has more metal ions than required by the ideal formula. This happens due to anion vacancies or by adding extra metal ions to interstitial sites. To maintain electrical neutrality, either electrons occupy the anion vacancies (F-centres) or extra electrons reside in interstitial sites.

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How do metal deficiency defects occur in a crystal?

Metal deficiency defects occur when a crystal has less metal ions than required by the ideal formula. This happens due to cation vacancies, which are usually compensated by adjacent metal ions with a higher positive charge.

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Study Notes

General Properties of Solids

  • Solids are a state of matter where constituents are firmly bound by strong forces.
  • Solids have definite mass, shape, and volume.
  • They are incompressible and rigid.
  • Solids have a close packed arrangement of particles.
  • Solids have high density but very slow diffusion.
  • Constituents have fixed positions, so only vibrational motion is possible.

Types of Solids

  • Crystalline solids: Constituents are arranged in a definite, repeating order over long distances.
  • They have flat faces and sharp edges with sharp melting points.
  • They show cleavage with fixed planes.
  • They are anisotropic (different physical properties in different directions due to the ordered arrangement of constituents).
  • Examples include CaF₂, ZnS, diamond, quartz, NaX
  • Amorphous solids: Constituents are not arranged in a regular or orderly manner for long distances.
  • They do not have sharp melting points.
  • They are pseudo solids.
  • They show isotropic behavior (same properties in all directions due to irregular arrangement).
  • They don't show cleavage.
  • Examples include glass, plastic, and rubber

Crystal Structure

  • Crystal: A homogeneous part of a solid substance with a regular, repeating pattern of structural units.
  • Crystal lattice: The regular arrangement of constituent particles (atoms, ions, etc.) in 3D space.
  • Face: A flat surface of a crystal.
  • Edge: Intersection of two adjacent faces.
  • Interfacial angle: Angle between two intersecting faces.

Types of Crystalline Solids (Detailed)

  • Ionic: Made of cations and anions with strong electrostatic forces. Very high melting points. Examples: NaCl, KCl.
  • Covalent (Network): Atoms connected by strong covalent bonds in a continuous network. Very high melting points. Examples: Diamond, graphite.
  • Molecular: Discrete molecules held together by weak intermolecular forces (van der Waals). Relatively low melting points. Examples: Ice, dry ice.
  • Metallic: Atoms connected by metallic bonds (delocalized electrons). Good conductors of heat and electricity. Variable melting points. Examples: All metals.

Bragg's Law

  • Max von Laue discovered that X-rays can diffract off crystals.
  • Bragg's law relates the wavelength of X-rays to the distance between crystal planes and the angle of reflection.

Unit Cells

  • Unit cell: The smallest repeating unit of a crystal lattice.
  • Different types of unit cells exist based on the arrangement of lattice points: Simple, body centred, face centred.

Packing Fractions

  • Packing fraction: The ratio of the volume occupied by constituent particles to the total volume of the unit cell.
  • Different packing fractions for different types of unit cells (Simple Cubic, Body-Centered Cubic, Face-Centered Cubic)

Coordination Number

  • Coordination number: The number of nearest neighbors surrounding a specific particle in the crystal
  • The coordination number depends upon the crystal structure.

Interstitial Voids

  • Interstitial voids: The spaces between the constituent particles in a close packed structure.
  • Two types of interstitial voids: Tetrahedral and octahedral voids.

Density of Lattice Matter

  • Density: The mass per unit volume.
  • Density calculation involves atoms, volume, and Avagadro's number.

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