This document discusses atomic structures and interatomic bonding. It begins by outlining the objectives and providing an outline of topics to be covered, including atomic models, electron configurations, the periodic table, and primary bonding types. It then delves into details of atomic structure including atomic number, mass, isotopes, and electron arrangements. The key bonding types of ionic, covalent and metallic are introduced and examples of each are provided. Ionic bonding involves transfer of electrons between metals and nonmetals, covalent bonding the sharing of electrons, and metallic bonding the sea of electrons in metal atoms.
1) Atoms bond through ionic, covalent, and metallic bonding depending on their positions on the periodic table and electronegativity differences.
2) Ionic bonding occurs between ions and involves electron transfer, covalent bonding involves sharing electrons between atoms, and metallic bonding arises from a "sea" of delocalized electrons between fixed ion cores.
3) Secondary intermolecular forces like hydrogen bonding and van der Waals forces provide weaker bonding between molecules.
The document summarizes Week 2 of an MME 323 materials science course focusing on atomic structure and interatomic bonding. It outlines the lecture topics which include atomic number, mass, and configuration, quantum numbers, the periodic table, and primary bonding types like ionic, covalent, and metallic. The learning objectives are to define key atomic concepts and describe different bonding mechanisms. Ionic bonding occurs between metals and non-metals and involves electron transfer. Covalent bonding is between non-metals and the sharing of electrons. Metallic bonding is within metals and due to positively charged metal ions in a "sea" of delocalized electrons.
Solids are characterized by their definite shape and also their considerable mechanical strength and rigidity. The particles that compose a solid material(with few exceptions), whether ionic, molecular, covalent or metallic, are held in place by strong attractive forces between them.
This document discusses crystal structures and their properties. It describes how atoms are arranged in crystalline solids through ordered unit cells that form a repeating lattice. The main crystal structures for metals are body-centered cubic, face-centered cubic, and hexagonal close-packed. It explains how to calculate properties like density from the unit cell parameters and atomic positions. Direction vectors are used to describe crystallographic directions.
The document provides information on crystal structures including:
- Crystalline solids have atoms arranged in an orderly, periodic manner while amorphous solids do not.
- Dense, regularly packed structures have lower energy than non-dense, randomly packed structures.
- A unit cell is the smallest repeating unit that defines the lattice structure. There are 14 possible Bravais lattice structures.
- Common crystal structures for metals include body centered cubic (BCC), face centered cubic (FCC), and hexagonal close packed (HCP).
- Properties of unit cells include the number of atoms, effective number of atoms, coordination number, and atomic packing factor.
This document discusses solid state physics and crystal structures. It begins by defining solid state physics as explaining the properties of solid materials by analyzing the interactions between atomic nuclei and electrons. It then discusses different types of solids including single crystals, polycrystalline materials, and amorphous solids. Single crystals have long-range periodic atomic order, while polycrystalline materials are made of many small crystals joined together and amorphous solids lack long-range order. The document goes on to describe crystal structures including crystal lattices, unit cells, and common crystal systems such as cubic, hexagonal, and orthorhombic. It provides examples of crystal structures including sodium chloride and its cubic lattice structure.
The document is a lecture on materials science and crystallography given by Hari Prasad. It begins by outlining the learning objectives which include differences between crystalline and non-crystalline structures, crystal systems, atomic packing factors, and unit cells. It then defines key concepts such as space lattices, unit cells, crystal systems, coordination number, and lattice parameters. Examples are provided of different crystal structures including simple cubic, body centered cubic, face centered cubic, and hexagonal close packed. Miller indices and how to determine plane intercepts are also discussed.
There are three main types of crystalline solids: ionic solids, molecular solids, and metallic solids. Ionic solids are composed of positive and negative ions arranged in a crystal lattice. They have properties like high melting points and are brittle. Molecular solids have molecules arranged in a particular configuration, and properties like low melting points and being nonconductors. Metallic solids have metal atoms or ions arranged in patterns, giving properties such as conductivity and malleability. All crystalline solids have constituents ordered in highly organized, repeating microscopic structures extending in three dimensions.
1) Atoms bond through ionic, covalent, and metallic bonding depending on their positions on the periodic table and electronegativity differences.
2) Ionic bonding occurs between ions and involves electron transfer, covalent bonding involves sharing electrons between atoms, and metallic bonding arises from a "sea" of delocalized electrons between fixed ion cores.
3) Secondary intermolecular forces like hydrogen bonding and van der Waals forces provide weaker bonding between molecules.
The document summarizes Week 2 of an MME 323 materials science course focusing on atomic structure and interatomic bonding. It outlines the lecture topics which include atomic number, mass, and configuration, quantum numbers, the periodic table, and primary bonding types like ionic, covalent, and metallic. The learning objectives are to define key atomic concepts and describe different bonding mechanisms. Ionic bonding occurs between metals and non-metals and involves electron transfer. Covalent bonding is between non-metals and the sharing of electrons. Metallic bonding is within metals and due to positively charged metal ions in a "sea" of delocalized electrons.
Solids are characterized by their definite shape and also their considerable mechanical strength and rigidity. The particles that compose a solid material(with few exceptions), whether ionic, molecular, covalent or metallic, are held in place by strong attractive forces between them.
This document discusses crystal structures and their properties. It describes how atoms are arranged in crystalline solids through ordered unit cells that form a repeating lattice. The main crystal structures for metals are body-centered cubic, face-centered cubic, and hexagonal close-packed. It explains how to calculate properties like density from the unit cell parameters and atomic positions. Direction vectors are used to describe crystallographic directions.
The document provides information on crystal structures including:
- Crystalline solids have atoms arranged in an orderly, periodic manner while amorphous solids do not.
- Dense, regularly packed structures have lower energy than non-dense, randomly packed structures.
- A unit cell is the smallest repeating unit that defines the lattice structure. There are 14 possible Bravais lattice structures.
- Common crystal structures for metals include body centered cubic (BCC), face centered cubic (FCC), and hexagonal close packed (HCP).
- Properties of unit cells include the number of atoms, effective number of atoms, coordination number, and atomic packing factor.
This document discusses solid state physics and crystal structures. It begins by defining solid state physics as explaining the properties of solid materials by analyzing the interactions between atomic nuclei and electrons. It then discusses different types of solids including single crystals, polycrystalline materials, and amorphous solids. Single crystals have long-range periodic atomic order, while polycrystalline materials are made of many small crystals joined together and amorphous solids lack long-range order. The document goes on to describe crystal structures including crystal lattices, unit cells, and common crystal systems such as cubic, hexagonal, and orthorhombic. It provides examples of crystal structures including sodium chloride and its cubic lattice structure.
The document is a lecture on materials science and crystallography given by Hari Prasad. It begins by outlining the learning objectives which include differences between crystalline and non-crystalline structures, crystal systems, atomic packing factors, and unit cells. It then defines key concepts such as space lattices, unit cells, crystal systems, coordination number, and lattice parameters. Examples are provided of different crystal structures including simple cubic, body centered cubic, face centered cubic, and hexagonal close packed. Miller indices and how to determine plane intercepts are also discussed.
There are three main types of crystalline solids: ionic solids, molecular solids, and metallic solids. Ionic solids are composed of positive and negative ions arranged in a crystal lattice. They have properties like high melting points and are brittle. Molecular solids have molecules arranged in a particular configuration, and properties like low melting points and being nonconductors. Metallic solids have metal atoms or ions arranged in patterns, giving properties such as conductivity and malleability. All crystalline solids have constituents ordered in highly organized, repeating microscopic structures extending in three dimensions.
[1] Crystal defects are irregularities in the structure of a crystal that arise from imperfect packing of atoms. There are several types of crystal defects including point defects, line defects, surface defects, and volume defects.
[2] Point defects are zero-dimensional and include vacancies, interstitial defects, Schottky defects, and Frenkel defects. Line defects are one-dimensional and include edge and screw dislocations. Surface defects are two-dimensional and include grain boundaries, twin boundaries, and stacking faults. Volume defects are three-dimensional voids or non-crystalline regions within the crystal structure.
1. Materials science is the study of relationships between the structure and properties of materials. It relates how the atomic and molecular structure of a material influences its properties.
2. A material's properties determine how it responds to external forces and the environment. Key properties include mechanical, electrical, thermal, optical, and chemical properties. Mechanical properties describe response to forces like strength and toughness.
3. There are three main classes of materials: metals, ceramics, and polymers. Metals are strong, ductile, and conductive. Ceramics are brittle but heat resistant. Polymers are lightweight and insulating. Materials science helps understand materials and design new components.
There are four basic atomic arrangements that determine the properties of metals: simple cubic, body-centered cubic, face-centered cubic, and hexagonal close-packed. The atomic packing factor, which represents the fraction of unit cell volume occupied by atoms, increases in the order of simple cubic, body-centered cubic, and face-centered cubic structures. Face-centered cubic has the highest atomic packing factor of 0.74 and is therefore the most dense arrangement. Different metallic crystal structures can explain variations in density and other material properties between metals.
This document provides an overview of high entropy alloys (HEAs). It discusses how HEAs were discovered in 1996 and research interest increased after 2004 papers by Yeh and Cantor. Key points include: HEAs have 5+ principal elements each between 5-35% concentration; entropy effect stabilizes solid solution phase; criteria for HEAs include parameters like entropy of mixing and valence electron concentration; four core effects are lattice distortion, sluggish diffusion, cocktail effect, and formation of solid solution phase. Examples of HEA applications discussed are coatings, bulk metallic glass, and refractory and carbide/cermet materials. The conclusion emphasizes that computational modeling of HEA properties could help address misconceptions about these materials.
Introduction to Materials Science & EngineeringAlif Haiqal
This document provides an overview of the course MSE XXX: Introduction to Materials Science & Engineering. It outlines the course objectives, which are to introduce fundamental concepts in materials science and engineering, including how material structure dictates properties and how processing can change structure. It describes the various components of the course, including lectures, recitations, laboratories, teaching assistants, textbooks, and websites. It provides a tentative schedule and overview of topics that will be covered over the 10 weeks. It also outlines the methods of assessment including quizzes, midterms and a final exam.
The document summarizes key concepts related to crystal structure:
Crystalline materials have atoms or molecules arranged in a regular, orderly 3D pattern which gives them high strength, while non-crystalline materials have a random arrangement and lower strength. A crystal structure is a regular repetition of this 3D pattern defined by a unit cell and space lattice. Common crystal structures include simple cubic, body-centered cubic, face-centered cubic, and hexagonal close-packed. Crystal defects such as point defects, dislocations, grain boundaries, and voids are also discussed.
Imperfections in solids can occur in the form of point defects, line defects, and plane defects. Point defects are irregularities around a single lattice point and include vacancies, interstitial atoms, and displaced atoms. There are different types of point defects based on whether they change the stoichiometry of the solid (stoichiometric defects) or introduce impurities (impurity defects). Stoichiometric defects preserve the overall composition of the solid and include vacancy defects, interstitial defects, Frenkel defects, and Schottky defects in ionic solids. Non-stoichiometric defects change the composition of the solid and lead to metal excess or metal deficiency.
Materials science and Engineering-IntroductionSanji Vinsmoke
Materials science and engineering involves investigating the relationships between the structures and properties of materials. Materials scientists develop new materials while materials engineers design materials to have specific properties. Virtually every aspect of modern life is influenced by materials in some way. The document discusses the four main material classes - metals, ceramics, polymers, and composites - and provides examples of common materials in each class as well as their typical properties. It also covers advanced materials areas like semiconductors, biomaterials, smart materials, and nanomaterials that are being developed to address modern needs.
The document provides information about crystal structures, including:
1) It discusses space lattices, which are arrangements of points that repeat periodically in 3D space, with every point having an identical surrounding. The smallest repeating unit of a lattice is called the primitive cell.
2) There are 14 possible crystal structures defined by unique combinations of lattice parameters (a, b, c values and α, β, γ angles). The structures differ in packing efficiency and symmetry.
3) Miller indices are used to specify crystallographic directions and planes, helping to understand properties that vary by orientation like strength and conductivity. Understanding planes and directions is important for predicting deformation and failure modes in materials.
Interatomic forces present in materials can predict their physical properties. Primary bonding involves valence electrons and includes ionic, covalent, coordinate covalent, and metallic bonds. Secondary bonding is weaker and includes London dispersion forces, polar molecule induced dipole bonds, and dipole-dipole bonds. Bonding energy and the shape of the potential energy curve between atoms varies between different materials and influences properties like melting temperature and thermal expansion.
CRYSTAL STRUCTURE AND ITS TYPES-SOLID STATE PHYSICSharikrishnaprabu
The document discusses crystal structures of solids. It defines crystalline and amorphous solids, and describes the ordered arrangement of atoms or molecules in crystalline solids that extends over long ranges. Crystalline solids are further classified based on the type of bonding between their constituents into ionic solids, covalent solids, molecular solids, and metallic solids. The document also describes unit cells, crystal lattices, Bravais lattices, and packing arrangements in crystals. Common crystal structures like sodium chloride and cesium chloride are presented as examples.
Space lattice, Unit cell, Bravais lattices (3-D), Miller indices, Lattice planes, Hexagonal closed packing (hcp) structure, Characteristics of an hcp cell, Imperfections in crystal: Point defects (Concentration of Frenkel and Schottky defects).
X – ray diffraction : Bragg’s law and Bragg’s spectrometer, Powder method, Rotating crystal method.
This document provides an overview of an introduction to materials science and engineering course. It outlines the required textbook, grading breakdown, and chapters to be covered. Chapter 1 introduces materials science and engineering and why it is studied. The main types of materials are described as metals, ceramics, polymers, and composites. Advanced materials like semiconductors and biomaterials are also mentioned. Relationships between structure, processing, and properties of materials are discussed.
Diffusion bonding is a solid-state welding technique that joins materials together through atomic diffusion without melting. It involves applying high pressure and moderate heat to join carefully cleaned and mated surfaces. Diffusion occurs in two stages - initial metal-to-metal contact formation followed by atomic diffusion and grain growth across the interface to form a complete bond. Various factors like temperature, pressure, time and surface preparation influence the diffusion rate. Common diffusion bonding methods include gas pressure bonding, vacuum fusion bonding and eutectic bonding. Diffusion bonding finds applications in the fabrication of components for industries like aerospace, nuclear and others.
This document discusses different types of defects in solids. There are two main types of defects - point defects and line defects. Point defects include vacancy defects, where lattice sites are vacant, and interstitial defects, where particles occupy interstitial positions. Point defects in stoichiometric crystals include Schottky defects and Frenkel defects. Non-stoichiometric crystals can have metal excess defects with anionic vacancies or excess cations at interstitial sites, or metal deficient defects with cation vacancies or extra anions at interstitial sites. Impurity defects occur when impurity ions are present at lattice sites or interstitial sites.
There are several types of imperfections or defects that can occur in crystal structures including point defects, line defects, interfacial defects, and bulk defects. Point defects include vacancies and interstitials which occur naturally in all crystals. Line defects are imperfections where rows of atoms have a differing structure, such as dislocations. Interfacial defects include grain boundaries and twin boundaries. The number and type of defects can be controlled and affect material properties, both positively and negatively.
Miller indices specify directions and planes in crystal lattices using integer indices. They are represented by sets of integers in parentheses that indicate the intercepts of a plane or direction with the lattice's basis vectors. For planes, the intercepts are taken as reciprocals and represented by (hkl). Directions are represented by [hkl] and families of directions by <hkl>. Miller indices allow unambiguous identification of planes and directions that influence material properties like optical behavior and reactivity.
1. Nuclear physics studies the composition and interactions of atomic nuclei. Nuclei are composed of protons and neutrons, which interact via the strong nuclear force.
2. Nuclear reactions such as fission, fusion, and radioactive decay involve changes in nuclear binding energies and mass defects. Fission releases energy as heavy nuclei split into lighter nuclei, while fusion releases energy by combining light nuclei into heavier ones.
3. Key concepts include the strong nuclear force, mass defect and binding energy, radioactive decay and half-lives, and the types of radiation involved in different nuclear reactions like fission and fusion.
- Crystallography is the study of crystalline solids using techniques like X-rays, electron beams, and neutron beams.
- In 1912, Max von Laue proved X-rays were diffracted by crystals, demonstrating diffraction patterns. He received the 1914 Nobel Prize in Physics for this discovery.
- In 1913, father and son team William and Lawrence Bragg developed Bragg's Law to explain X-ray diffraction by crystals and their invention of the X-ray spectroscope earned them the 1914 Nobel Prize in Physics.
There are several types of defects that can arise in solids, including point defects like vacancies and interstitials, line defects like dislocations, and area defects like grain boundaries. The number and type of defects can be controlled through processing parameters and affect the material properties. While some defects are undesirable, others can play important roles like enabling plastic deformation through dislocation motion. Advanced microscopy techniques allow direct imaging of these defect structures at atomic scales.
The document discusses the crystal structure of materials and different types of bonds in solids. It describes metallic, ionic, covalent and network bonding. It discusses properties of materials formed by different bond types. It also covers crystal structures, Miller indices, Bragg's law, X-ray diffraction, structural imperfections and crystal growth. Energy band theory is introduced to classify materials as conductors, insulators or semiconductors based on their electron configurations.
This document discusses the crystal structure of materials and different types of bonds in solids. It describes metallic, ionic, covalent, and network solids. Metallic solids are held together by delocalized electrons forming a 'electron soup'. Ionic bonds occur through electron transfer between metals and non-metals. Covalent bonds involve electron sharing. Network solids form extensive 1D, 2D or 3D networks through covalent bonds. The properties of these materials depend on the type of bonding. The document also discusses crystal structure, unit cells, packing factors, Miller indices, Bragg's law and uses of X-ray crystallography.
[1] Crystal defects are irregularities in the structure of a crystal that arise from imperfect packing of atoms. There are several types of crystal defects including point defects, line defects, surface defects, and volume defects.
[2] Point defects are zero-dimensional and include vacancies, interstitial defects, Schottky defects, and Frenkel defects. Line defects are one-dimensional and include edge and screw dislocations. Surface defects are two-dimensional and include grain boundaries, twin boundaries, and stacking faults. Volume defects are three-dimensional voids or non-crystalline regions within the crystal structure.
1. Materials science is the study of relationships between the structure and properties of materials. It relates how the atomic and molecular structure of a material influences its properties.
2. A material's properties determine how it responds to external forces and the environment. Key properties include mechanical, electrical, thermal, optical, and chemical properties. Mechanical properties describe response to forces like strength and toughness.
3. There are three main classes of materials: metals, ceramics, and polymers. Metals are strong, ductile, and conductive. Ceramics are brittle but heat resistant. Polymers are lightweight and insulating. Materials science helps understand materials and design new components.
There are four basic atomic arrangements that determine the properties of metals: simple cubic, body-centered cubic, face-centered cubic, and hexagonal close-packed. The atomic packing factor, which represents the fraction of unit cell volume occupied by atoms, increases in the order of simple cubic, body-centered cubic, and face-centered cubic structures. Face-centered cubic has the highest atomic packing factor of 0.74 and is therefore the most dense arrangement. Different metallic crystal structures can explain variations in density and other material properties between metals.
This document provides an overview of high entropy alloys (HEAs). It discusses how HEAs were discovered in 1996 and research interest increased after 2004 papers by Yeh and Cantor. Key points include: HEAs have 5+ principal elements each between 5-35% concentration; entropy effect stabilizes solid solution phase; criteria for HEAs include parameters like entropy of mixing and valence electron concentration; four core effects are lattice distortion, sluggish diffusion, cocktail effect, and formation of solid solution phase. Examples of HEA applications discussed are coatings, bulk metallic glass, and refractory and carbide/cermet materials. The conclusion emphasizes that computational modeling of HEA properties could help address misconceptions about these materials.
Introduction to Materials Science & EngineeringAlif Haiqal
This document provides an overview of the course MSE XXX: Introduction to Materials Science & Engineering. It outlines the course objectives, which are to introduce fundamental concepts in materials science and engineering, including how material structure dictates properties and how processing can change structure. It describes the various components of the course, including lectures, recitations, laboratories, teaching assistants, textbooks, and websites. It provides a tentative schedule and overview of topics that will be covered over the 10 weeks. It also outlines the methods of assessment including quizzes, midterms and a final exam.
The document summarizes key concepts related to crystal structure:
Crystalline materials have atoms or molecules arranged in a regular, orderly 3D pattern which gives them high strength, while non-crystalline materials have a random arrangement and lower strength. A crystal structure is a regular repetition of this 3D pattern defined by a unit cell and space lattice. Common crystal structures include simple cubic, body-centered cubic, face-centered cubic, and hexagonal close-packed. Crystal defects such as point defects, dislocations, grain boundaries, and voids are also discussed.
Imperfections in solids can occur in the form of point defects, line defects, and plane defects. Point defects are irregularities around a single lattice point and include vacancies, interstitial atoms, and displaced atoms. There are different types of point defects based on whether they change the stoichiometry of the solid (stoichiometric defects) or introduce impurities (impurity defects). Stoichiometric defects preserve the overall composition of the solid and include vacancy defects, interstitial defects, Frenkel defects, and Schottky defects in ionic solids. Non-stoichiometric defects change the composition of the solid and lead to metal excess or metal deficiency.
Materials science and Engineering-IntroductionSanji Vinsmoke
Materials science and engineering involves investigating the relationships between the structures and properties of materials. Materials scientists develop new materials while materials engineers design materials to have specific properties. Virtually every aspect of modern life is influenced by materials in some way. The document discusses the four main material classes - metals, ceramics, polymers, and composites - and provides examples of common materials in each class as well as their typical properties. It also covers advanced materials areas like semiconductors, biomaterials, smart materials, and nanomaterials that are being developed to address modern needs.
The document provides information about crystal structures, including:
1) It discusses space lattices, which are arrangements of points that repeat periodically in 3D space, with every point having an identical surrounding. The smallest repeating unit of a lattice is called the primitive cell.
2) There are 14 possible crystal structures defined by unique combinations of lattice parameters (a, b, c values and α, β, γ angles). The structures differ in packing efficiency and symmetry.
3) Miller indices are used to specify crystallographic directions and planes, helping to understand properties that vary by orientation like strength and conductivity. Understanding planes and directions is important for predicting deformation and failure modes in materials.
Interatomic forces present in materials can predict their physical properties. Primary bonding involves valence electrons and includes ionic, covalent, coordinate covalent, and metallic bonds. Secondary bonding is weaker and includes London dispersion forces, polar molecule induced dipole bonds, and dipole-dipole bonds. Bonding energy and the shape of the potential energy curve between atoms varies between different materials and influences properties like melting temperature and thermal expansion.
CRYSTAL STRUCTURE AND ITS TYPES-SOLID STATE PHYSICSharikrishnaprabu
The document discusses crystal structures of solids. It defines crystalline and amorphous solids, and describes the ordered arrangement of atoms or molecules in crystalline solids that extends over long ranges. Crystalline solids are further classified based on the type of bonding between their constituents into ionic solids, covalent solids, molecular solids, and metallic solids. The document also describes unit cells, crystal lattices, Bravais lattices, and packing arrangements in crystals. Common crystal structures like sodium chloride and cesium chloride are presented as examples.
Space lattice, Unit cell, Bravais lattices (3-D), Miller indices, Lattice planes, Hexagonal closed packing (hcp) structure, Characteristics of an hcp cell, Imperfections in crystal: Point defects (Concentration of Frenkel and Schottky defects).
X – ray diffraction : Bragg’s law and Bragg’s spectrometer, Powder method, Rotating crystal method.
This document provides an overview of an introduction to materials science and engineering course. It outlines the required textbook, grading breakdown, and chapters to be covered. Chapter 1 introduces materials science and engineering and why it is studied. The main types of materials are described as metals, ceramics, polymers, and composites. Advanced materials like semiconductors and biomaterials are also mentioned. Relationships between structure, processing, and properties of materials are discussed.
Diffusion bonding is a solid-state welding technique that joins materials together through atomic diffusion without melting. It involves applying high pressure and moderate heat to join carefully cleaned and mated surfaces. Diffusion occurs in two stages - initial metal-to-metal contact formation followed by atomic diffusion and grain growth across the interface to form a complete bond. Various factors like temperature, pressure, time and surface preparation influence the diffusion rate. Common diffusion bonding methods include gas pressure bonding, vacuum fusion bonding and eutectic bonding. Diffusion bonding finds applications in the fabrication of components for industries like aerospace, nuclear and others.
This document discusses different types of defects in solids. There are two main types of defects - point defects and line defects. Point defects include vacancy defects, where lattice sites are vacant, and interstitial defects, where particles occupy interstitial positions. Point defects in stoichiometric crystals include Schottky defects and Frenkel defects. Non-stoichiometric crystals can have metal excess defects with anionic vacancies or excess cations at interstitial sites, or metal deficient defects with cation vacancies or extra anions at interstitial sites. Impurity defects occur when impurity ions are present at lattice sites or interstitial sites.
There are several types of imperfections or defects that can occur in crystal structures including point defects, line defects, interfacial defects, and bulk defects. Point defects include vacancies and interstitials which occur naturally in all crystals. Line defects are imperfections where rows of atoms have a differing structure, such as dislocations. Interfacial defects include grain boundaries and twin boundaries. The number and type of defects can be controlled and affect material properties, both positively and negatively.
Miller indices specify directions and planes in crystal lattices using integer indices. They are represented by sets of integers in parentheses that indicate the intercepts of a plane or direction with the lattice's basis vectors. For planes, the intercepts are taken as reciprocals and represented by (hkl). Directions are represented by [hkl] and families of directions by <hkl>. Miller indices allow unambiguous identification of planes and directions that influence material properties like optical behavior and reactivity.
1. Nuclear physics studies the composition and interactions of atomic nuclei. Nuclei are composed of protons and neutrons, which interact via the strong nuclear force.
2. Nuclear reactions such as fission, fusion, and radioactive decay involve changes in nuclear binding energies and mass defects. Fission releases energy as heavy nuclei split into lighter nuclei, while fusion releases energy by combining light nuclei into heavier ones.
3. Key concepts include the strong nuclear force, mass defect and binding energy, radioactive decay and half-lives, and the types of radiation involved in different nuclear reactions like fission and fusion.
- Crystallography is the study of crystalline solids using techniques like X-rays, electron beams, and neutron beams.
- In 1912, Max von Laue proved X-rays were diffracted by crystals, demonstrating diffraction patterns. He received the 1914 Nobel Prize in Physics for this discovery.
- In 1913, father and son team William and Lawrence Bragg developed Bragg's Law to explain X-ray diffraction by crystals and their invention of the X-ray spectroscope earned them the 1914 Nobel Prize in Physics.
There are several types of defects that can arise in solids, including point defects like vacancies and interstitials, line defects like dislocations, and area defects like grain boundaries. The number and type of defects can be controlled through processing parameters and affect the material properties. While some defects are undesirable, others can play important roles like enabling plastic deformation through dislocation motion. Advanced microscopy techniques allow direct imaging of these defect structures at atomic scales.
The document discusses the crystal structure of materials and different types of bonds in solids. It describes metallic, ionic, covalent and network bonding. It discusses properties of materials formed by different bond types. It also covers crystal structures, Miller indices, Bragg's law, X-ray diffraction, structural imperfections and crystal growth. Energy band theory is introduced to classify materials as conductors, insulators or semiconductors based on their electron configurations.
This document discusses the crystal structure of materials and different types of bonds in solids. It describes metallic, ionic, covalent, and network solids. Metallic solids are held together by delocalized electrons forming a 'electron soup'. Ionic bonds occur through electron transfer between metals and non-metals. Covalent bonds involve electron sharing. Network solids form extensive 1D, 2D or 3D networks through covalent bonds. The properties of these materials depend on the type of bonding. The document also discusses crystal structure, unit cells, packing factors, Miller indices, Bragg's law and uses of X-ray crystallography.
The document discusses molecular orbital theory and atomic orbitals. It explains that molecular orbitals are formed from the overlapping and combination of atomic orbitals from individual atoms. The molecular orbitals encompass the entire molecule and electrons occupy these molecular orbitals rather than being localized to individual bonds. Molecular orbital diagrams are presented for several diatomic and polyatomic molecules, showing the bonding, non-bonding, and antibonding molecular orbitals formed from the atomic orbital combinations.
The periodic table arranges elements based on electron configuration in atoms. Elements in the same group have similar valence electron structures and chemical properties. Electrons fill atomic orbitals according to the Aufbau principle and Hund's rule. Valence electrons determine how elements bond and react. Ion charges form when atoms gain or lose valence electrons to achieve stable full shells like noble gases. Magnetism results from aligned spins of unpaired electrons.
Atomic Structure and chemical BONDING.pptxSesayAlimamy
This document discusses fundamentals of atomic structure and interatomic bonding. It covers topics like atomic models, quantum numbers, electron configurations, and the periodic table. The key types of atomic bonding are also summarized, including ionic, covalent, metallic, hydrogen and van der Waals bonds. Interatomic forces are described as a function of separation distance, including both attractive and repulsive forces.
element of matter – The Atom, Bohr Model, Heisenberg’s uncertainty principlegkumarouct
In order to understand the structure of materials and its
correlation to property, we have to start form the basic
element of matter – The Atom,
The Bohr Model, Heisenberg’s uncertainty principle, Laws of Quantum mechanics, Orbital shape and quantum numbers, Atomic Bonding, Lennard-Jones potential
Applied Chemistry, atomic and molecular structure, part 1, by Shiraz mahbob PhDMaqsoodAhmadKhan5
applied chemistry lecture and slide,
Applied Chemistry, atomic and molecular structure, part 1, by Shiraz mahbob PhD, lecturer in chemistry in pakistan institute of engineering and applied sciences
Class 11 Chapter 4 Chemical Bonding and Molecular Structure.pptxRajnishPrasadSarma
This document provides an overview of chemical bonding and molecular structure. It discusses topics such as octet rule, covalent bonds, limitations of the octet rule, ionic or electrovalent bonds, lattice enthalpy, bond parameters including bond length, bond angle, bond enthalpy and bond order. It also covers concepts of resonance, polar covalent bonds, dipole moment and covalent character in ionic bonds based on Fajans' rule. The document is presented as part of a Class XI chemistry curriculum on this unit.
The document discusses atomic structure and bonding. It describes the structure of atoms including protons, neutrons, and electrons. It explains how atomic number determines the element and how isotopes have the same number of protons but different neutrons. Electron configuration and quantum numbers are also summarized. The three main types of bonds - ionic, covalent, and metallic - are introduced along with how they influence material properties.
This document provides an overview of organic chemistry concepts including:
- The electronic structure of atoms and how this relates to bonding
- Different types of bonds (ionic, covalent, polar, nonpolar) and how they form
- Lewis structures and resonance forms
- Molecular shapes determined by hybridization of orbitals
- Isomerism including constitutional and geometric isomers
The document covers fundamental topics that provide context for understanding organic molecular structures and reactions.
The document discusses chemical bonding, including the formation of ions, ionic bonds, metallic bonds, and covalent bonds. Ions are formed when atoms gain or lose electrons to obtain full outer electron shells. Ionic bonds form when ions of opposite charge attract via electrostatic forces. Metallic bonds occur via delocalized electrons within metal atoms. Covalent bonds form through the sharing of electron pairs between nonmetal atoms. The octet rule and electronegativity help explain bonding properties.
1) Atoms are the basic units of matter and contain protons, neutrons, and electrons. Elements are substances made of only one type of atom, while compounds contain two or more different elements.
2) Crystalline solids consist of atoms arranged in repeated patterns called unit cells. The three main crystal structures are body-centered cubic, face-centered cubic, and hexagonal close-packed.
3) Atomic bonding in solids includes ionic bonding between oppositely charged ions, covalent bonding through electron sharing, and metallic bonding from a "sea" of delocalized electrons binding positive ions.
1) Atoms are the building blocks of matter and are composed of a nucleus containing protons and neutrons surrounded by electrons that orbit in shells.
2) There are different subatomic particles that make up an atom including protons, neutrons, and electrons. Protons and neutrons are in the nucleus while electrons orbit in shells around the nucleus.
3) Isotopes are atoms of the same element that have differing numbers of neutrons. For example, hydrogen has isotopes of deuterium and tritium that have extra neutrons compared to common hydrogen.
The document summarizes the four quantum numbers that describe electrons: principal quantum number (n), angular momentum quantum number (l), magnetic quantum number (ml), and spin quantum number (ms). It then discusses electron configuration, which is the arrangement of electrons in an atom based on the Aufbau principle, Pauli exclusion principle, and Hund's rule. Electron configuration can be written using symbols, orbital diagrams, noble gas notation, and electron-dot structures.
Materials science and engineering involves the study of atomic structure and bonding in materials. There are three primary types of atomic bonding - ionic, covalent, and metallic. Crystalline solids can have face-centered cubic (FCC), body-centered cubic (BCC), or hexagonal close-packed (HCP) crystal structures which influence material properties. Crystalline materials can assemble into either crystalline or amorphous structures, and material properties depend on crystal orientation in single crystals but are isotropic in polycrystalline materials with randomly oriented grains.
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3. Objectives
• To be able to name two atomic models cited, and note the differences
between them.
• To describe the important quantum-mechanical principle that relates
to electron energies.
• Briefly describe ionic, covalent, metallic, hydrogen and van der Waals
bonds.
• Note which material exhibit each of these bonding types
4. Outline
• Fundamental Concepts
• Atomic Models
• Quantum Numbers
• Electron Configurations
• Periodic Table
• Atomic Bonding in Solids
• Bonding forces and Energies
• Primary interatomic bonds (ionic, covalent & metallic)
• Secondary bonding
5. Fundamental Concepts
• Basic Idea:
Properties of materials are a
consequence of
• Identity of the atoms
• Spatial arrangement of the
atoms
• Interaction between the atoms
• Thus, the need to study atomic
structure/bonding.
6. Atom
• Consists of very small nucleus composed of protons
and neutrons, which is encircles or orbited by
moving electrons.
8. Atomic Number (Z)
• For an electrically neutral or complete
atom, the atomic number also equals
the number of electrons.
Example
• Uranium (Z = 92) - The highest of the
naturally occurring elements
9. Atomic Mass (A)
Sum of the masses of protons
and neutrons; atomic mass
unit = amu = 1/12 mass of 12C
10. Isotopes
• Atoms that have two or more different atomic masses due to variable
number of neutrons (N)
• A ≈ Z + N
11. Atomic Weight
• Weighted average of the atomic masses of the atom’s naturally
occurring isotopes.
• It may be expresses in terms of atomic mass units or an atomic basis,
or the mass per mole of atoms.
• Atomic wt = wt of 6.022 x 1023 molecules or atoms
(Unit for atomic weight /mass)
• 1 amu/atom = 1g/mol
• C 12.011
• H 1.008
12. Atom VS Molecules
Atom
• An atom is smallest particle in an
element that has the properties of
the element.
• It is not possible to breakdown the
atom further retaining the
properties of the element.
• Atoms are not visible to the naked
eye and are the basic building
blocks.
Molecule
• Molecules are formed by the
combination of two or more
atoms.
• Unlike atoms, A molecules can be
subdivided to individual atoms.
• Molecules also are not visible to
the naked eye, while can be seen
through highly magnifying
microscopes and other scientific
devices.
Water is comprised of numerous water molecules. Each water molecule is made up of one oxygen atom and
two hydrogen atoms.
13. Electrons in Atoms
• The electrons form a cloud around the nucleus,
of radius of around 0.05-2nm.
• Bohr Atomic Model (Quantum theory)
• 1st JJ Thomson
• 2nd Ernest Rutherford
• 3rd Niels Bohr
15. Energy Levels
• Energy of electrons is quantized,
meaning that the electrons are
permitted to have only specific values
of energy.
• Energy level or states – an electron may
change energy, it must make a
quantum jump either to an allowed
higher energy (with absorption of
energy) or to a lower energy (with
emission of energy).
17. Quantum Mechanics
• A branch of physics that deals with
atomic and subatomic systems; it
allows only discrete values of energy
that are separated from one another.
18. • Electrons do not revolve around circular orbits, but in odd shaped
orbitals depending on their quantum number.
• Compared with classical mechanics, which allows continuous energy
values.
• Limitations of the Bohr atomic model - Its inability to explain several
phenomena involving electrons.
20. Quantum
Numbers
• A set of four numbers, the values of which are used to label possible electron states.
• The four parameters that characterized the electron in an atom are:
• size (integer)
• shape (integer)
• spatial orientation (integer)
• energy levels
• Dictates the number of states within each subshell.
21. Quantum Numbers
• Principal (n) - n = 1, 2, 3, 4, 5….
• Describes the electron shell, or
energy level, of an atom.
• The value of n ranges from 1 to the
shell containing the outermost
electron of that atom
• The distance of an electron from
the nucleus, or its position
Example
• For caesium (Cs), the
outermost valence electron
is in the shell with energy
level 6, so an electron in
caesium can have an n value
from 1 to 6.
22.
23. Quantum Numbers
• Angular or Azimuthal (L) – L = s, p, d, f
• (also known as the angular quantum number or orbital quantum number)
describes the subshell, and gives the magnitude of the orbital angular
momentum through the relation:
• L2 = ħ2 ℓ (ℓ + 1).
• Gives the shape of the orbital /electron subshell.
• The orbital angular momentum quantum number ℓ (little “el”)
• Planck's constant 6.62607015 × 10−34 joule per second.
24. Quantum Numbers
• Magnetic (m) – s = 1, p = 3, d = 5, f == 7
• Describes the specific orbital (or "cloud") within that subshell, and yields the
projection of the orbital angular momentum along a specified axis:
• Lz = mℓ ħ.
• Gives the number of energy states for each subshell.
• In the absence of an external magnetic field, the states within each shell are
identical.
• When a magnetic field is applied, these subshell states split, with each state
assuming a slightly different energy.
25. Quantum Numbers
• Spin moment (s)
• Describes the spin (intrinsic angular momentum) of the electron within that
orbital, and gives the projection of the spin angular momentum S along the
specified axis:
• Sz = ms ħ.
26.
27.
28. Electron configurations
• Electron state (level)
• One of the set of discrete, quantized
energies that are allowed for electrons.
• In the atomic case each state is specified
by four quantum numbers.
30. Relative energies of
Electrons
• Figure 2.4 schematic representation of
the relative energies of the electrons for
the various shells and subshells.
(Introduction to Materials Science and
Engineering, J.M. Ralls, T.H. Courtney and
J. Wulff)
31. Relative energies of
Electrons
From Figure 2.4
• The smaller the principal quantum
number, the lower the energy level.
Example. 1s < 2s < 3s
• Within each shell, the energy of a
subshell level increases with the value
of the l quantum number.
Example. 3s < 3p < 3d
32. Relative energies of
Electrons
There may be overlap in energy of a state
in one shell with states in an adjacent
shell, which is especially true of d and f
states.
Example. 4s < 3d
For most atoms, the electrons fill up the
lowest possible energy states in the
electron shells and subshells, two
electrons with opposite signs per state.
33. Ground State
• A condition when all the electrons occupy the lowest possible
energies in accord with the foregoing restrictions.
• A normally filled electron energy state form which an electron
excitation may occur.
34. Ground State
Example
• Figure 2.5 Schematic representation of
the filled and lowest unfilled energy
states for a sodium atom.
35. Electron Configuration
(structure of an atom)
• For an atom, it is the manner in which possible
electron state are filled with electrons.
• The number of electrons in each subshell is
indicated by a superscript after the shell-subshell
designation.
• Table 2.2 Listing of the expected electron
configuration for some of the common elements.
Callister
36. Valence electrons
• The electrons in the
outermost occupied
electron shell, which
participates in
interatomic bonding.
37. Stable Electron
Configurations
• The states within the outermost or valence electrons
shell are completely filled.
Example.
Neon (Ne), Argon (Ar), Krypton (Kr), Helium (He) – these
elements are inert, or noble gases, which are virtually
chemically unreactive.
Some atoms of the elements that have unfilled valence
shells assume stable electron configurations by gaining or
losing electrons to form charged ions, by sharing
electrons with other atoms.
39. The Periodic Table
• The arrangement of the chemical elements with increasing atomic
number according to the periodic variations in electron structure.
• Nonmetallic elements are positioned at the far right side of the table.
40. Figure 2.6 the periodic table of the elements. The numbers in parentheses are the atomic weights of the most stable or
common isotopes.
41. Arrangement:
• Rows or Periods
7 horizontal rows arranged in increasing atomic number.
• Columns or Groups
Have similar valence electron structures, as well as chemical and
physical properties.
42. Groups in the Periodic Table
• Group IA (alkali metals)
Elements are one electron in excess of stable structures..
• Group IIA (alkaline earth metals)
Elements are two electrons in excess of stable structures.
• Group IIIB through IIB (transition metals)
Have partially filled electron states and in some case, one or two
electrons in the next higher energy shell.
• Group IIIA, IVA, VA
Display characteristics that are intermediate between the metals and
nonmetals by virtue of the valence electron structures.
43. Groups in the Periodic Table
• Group VIA
Elements are two electrons deficient from having stable
structures.
• Group VIIA (halogens)
Elements are one electron deficient from having stable
structures.
• Group O (inert gases)
Elements have filled electron shells and stable electron
configurations.
Inert – lacking the ability to move
– chemically inactive
44. Electro-positive
• They are capable of giving up their few valence electrons to become
positively charged ions.
Electro-negative
• They readily accept electrons to become negatively charged ions, or
sometimes share electrons with other forms.
45. Figure 2.7 the electronegativity values for the elements. (The nature of the Chemical Bond, 3rd ed. Linus Pauling)
46. Electro-negative
Elements
• Conversely, the closer the atoms are
together (i.e. the smaller the difference
in electronegativity), the greater the
degree of co-valency.
• Atoms are more likely to accept
electrons if their outer shells are almost
full, and if they are less “Shielded” from
or closer to the nucleus.
48. Atomic Bonding in
Solids
• The principles of atomic bonding are best
illustrated by considering how tow isolated
atoms interact as they are brought close
together from an infinite separation.
• Large distances
• Interactions are negligible.
• The atoms are too far apart to have an
influence on each other.
• Small distances
• Each atom exerts forces on each other.
• The magnitude of each depends on the
separation or interatomic distance, r.
• Equilibrium Spacing (r0)
• The centers of two atoms will remain
separated even at equilibrium.
49. Bonding energy (E0)
• The minimum net energy that corresponds to the equilibrium
spacing.
• The energy that would be required to separate two atoms to an
infinite separation.
50. Bonding energy (E0)
• Figure 2.8 (a) The dependence of repulsive,
attractive, and net forces on interatomic separation
for two isolated atoms. (b) The dependence of
repulsive, attractive and net potential energies on
interatomic separation for two isolated atoms.
51. Electron Volt
• An energy unit that is convenient for describing atomic bonding.
• It is the energy gained or lost by an electron
53. Bonds found in solids.
• The bonding that involves the valence electrons.
• The nature of the bond depends on the electron structure of the
constituent atoms.
• Each of the three types of primary bonding arises from the tendency
of the atoms to assume stable electron structures, like those of the
inert gases, by completely filling the outermost electron shell.
• Why Atoms bond? - to lower their energy
54. Ionic Bonding
• Type of bonding between metals and non-metals.
• Elements that are suited for this type of bonding are located at the
horizontal extremities of the periodic table.
• Atoms of metals easily give up their valence electrons to their non-
metallic counterpart, thus we have a transfer of electrons
• In the process, all the atoms acquire stable or inert gas
configurations; also, they acquire an electrical charge, thus becoming
ions.
55. Ionic Bonding
• Let’s take the prevalent example of the
Sodium Chloride (NaCl), where the
outermost orbit of the sodium has one
electron, while chlorine has seven
electrons in the outermost shell.
• So, Chlorine needs only one electron to
complete its octet. When the two atoms
(Na and Cl) are put close to each other,
the sodium donates its electron to
chlorine. Thus by losing one electron
sodium becomes positively charged and
by accepting one electron chlorine
becomes negatively charged and becomes
chloride ion.
56. Ionic Bonding
• A sodium atom can assume the
electron configuration of neon
(with a net single + charge) by
the transfer of its one valence 3s
electron to the chlorine atom.
Aster the transfer, the chlorine
now has a net negative charge
with an electron configuration of
argon
57. Ionic Bonding
• Attractive forces are coulombic, meaning due to the positive and
negative ions, they attract one another.
• Large differences in electronegativity
• Non-directional type – the magnitude of the bond is equal in all
directions around the ion.
• Bonded atoms preferred specific orientations, have definite shape.
• For ionic materials to be stable, all positive ions mush have as nearest
neighbors negatively charged ions in a three dimensional scheme and
vice-versa.
58. Covalent Bonding
• Stable electron configurations are achieved by sharing of electrons
between adjacent atoms.
• The two atoms involved will each contribute at least one electron to
the bond.
• Comparable electronegativity
• Directional type
59. Covalent
Bonding
• Covalent bonds involve the sharing of the
electrons between the atoms. The pairing
of the shared electron, produce a new
orbit around the nuclei of both the atoms
referred to as molecule.
• For example, water having the formula as
H2O, in this the covalent bond is between
each hydrogen and oxygen molecules,
where two electrons are shared between
hydrogen and oxygen, one from each.
• As a hydrogen molecule, H2 contains two
hydrogen atom which is linked by the
covalent bond with oxygen. These are the
attractive forces between the atoms
occurring in the outer most orbit of the
electrons.
60. Covalent Bonding
• for a molecule of methane (CH4). The carbon
atom has four valence electrons, whereas each
of the four hydrogen atoms has a single
valence electron. Each hydrogen atom can
acquire a helium electron configuration (two 1s
valence electrons) when the carbon atom
shares with it one electron.
• The carbon now has four additional shared
electrons, one from each hydrogen, for a total
of eight valence electrons, and the electron
structure of neon. The covalent bond is
directional; that is, it is between specific atoms
and may exist only in the direction between
one atom and another that participates in the
electron sharing.
61. % Ionic Character
• It is possible to have interatomic bonds that are partially ionic and
partially covalent, and, in fact, very few compounds exhibit pure ionic
or covalent bonding. For a compound, the degree of either bond type
depends on the relative positions of the constituent atoms in the
periodic table or the difference in their electronegativities.
• The wider the separation (both horizontally—relative to Group IVA—
and vertically) from the lower left to the upper right-hand corner (i.e.,
the greater the difference in electronegativity), the more ionic the
bond.
• Conversely, the closer the atoms are together (i.e., the smaller the
difference in electronegativity), the greater the degree of covalency.
62. % Ionic Character
• The percent ionic character (%IC) of a bond between elements A and
B (A being the most electronegative) may be approximated by the
expression
where
Xa, Xb - electronegativity
- from Pauling’s table of electronegativities
= [1 – e ] x 100%
-0.25(Xa – Xb) 2
63. % Ionic Character
• Example
Given: XCl = 3.0, XH = 2.1, XNa = 0.9
Find:
(1) Determine the % ionic character of HCL, NaCl and Cl2;
(2) rank the bonds in HCL, NaCl and Cl2 from most covalent to most ionic
Ans.
(1)Cl2 – 0 difference
HCL = {1 –exp[-0.25 (2.1 – 3.0)2]} x 100%
= 18% ionic
NaCl= {1 –exp[-0.25 (0.9 – 3.0)2]} x 100%
= 67% ionic
(2) Cl2 > HCl > NaCl - differences in electronegativities
64. Metallic bonding
• Valence e- drifting through the entire metal to form a sea (cloud) of
electrons
• Sharing of electrons
• Comparable electronegativity
• Non-directional type
65. Metallic bonding
• Due to the presence of the delocalized or free-electrons of the
valence electrons, Paul Drude came up with the name “sea of
electrons” in 1900. The various characteristics properties of the
metals are; they have high melting and boiling points, they are
malleable and ductile, good conductors of the electricity, strong
metallic bonds, and low volatility.
• In this type, the valence electrons continuously move from one atom
to other as the outermost shell of electrons of each metal atoms
overlaps the neighboring atoms. So we can say that the in metal the
valence electrons continuously moves independently from one place
to another throughout the entire space.
67. Metallic bonding
• A. Outermost electrons wander freely
through metal. Metal consists of cations
held together by negatively-charged
electron "glue."
68. Metallic bonding
• B. Free electrons can move rapidly in
response to electric fields, hence metals
are a good conductor of electricity.
69. Metallic bonding
• C. Free electrons can transmit kinetic
energy rapidly, hence metals are good
conductors of heat.
70. Metallic bonding
• D. The layers of atoms in metal are hard
to pull apart because of the electrons
holding them together, hence metals
are tough. But individual atoms are not
held to any other specific atoms, hence
atoms slip easily past one another. Thus
metals are ductile. Metallic Bonding is
the basis of our industrial civilization.
71. Comparison Chart
BASIS FOR COMPARISON COVALENT BOND METALLIC BOND IONIC BOND
Meaning When there is a strong
electrostatic force of
attractions between two
positively charged nuclei
and the shared pair of
electrons is called the
covalent bond.
When there is the strong
electrostatic force of
attractions between the
cation or atoms and the
delocalized electrons in
the geometrical
arrangement of the two
metals, is called a metallic
bond.
When there is a strong
electrostatic force of
attraction between a
cation and an anion (two
oppositely charged ions)
of elements is called the
ionic bond. This bond is
formed between a metal
and a non-metal.
Existence Exist as solids, liquids and
gasses.
Exist in the solid state
only.
They also exist in the solid
state only.
Occurs between Between two non-metals. Between two metals. Non-metal and metal.
72. Comparison Chart
BASIS FOR COMPARISON COVALENT BOND METALLIC BOND IONIC BOND
Involves Sharing of electrons in the
valence shell.
The attraction between
the delocalized electrons
present in the lattice of
the metals.
Transfer and accepting of
electrons from the
valence shell.
Conductivity Very low conductivity. High thermal and
electrical conductivity.
Low conductivity.
Hardness These are not very hard,
though exceptions are
silicon, diamond and
carbon.
These are not hard. These are hard, because
of the crystalline nature.
73. Comparison Chart
BASIS FOR COMPARISON COVALENT BOND METALLIC BOND IONIC BOND
Melting and Boiling Points Low. High. Higher.
Malleability and Ductility These are non-malleable
and non-ductile.
Metallic bonds are
malleable and ductile.
Ionic bonds are also non-
malleable and non-
ductile.
Bond They are the directional
bond.
The bond is non-
directional.
The bond is non-
directional.
74. Comparison Chart
BASIS FOR COMPARISON COVALENT BOND METALLIC BOND IONIC BOND
Bond energy Higher than the metallic
bond.
Lower than the other two
bond.
Higher than the metallic
bond.
Electronegativity Polar covalent: 0.5-1.7;
Non-polar<0.5.
Not available.
>1.7.
Examples Diamond, carbon, silica,
hydrogen gas, water,
nitrogen gas, etc.
Silver, gold, nickel, copper,
iron, etc.
NaCl, BeO, LiF, etc.
75. Secondary, van der Waals, or physical bonds
• Interatomic and intermolecular bonds that is relatively weak in
comparison to primary or chemical bonds.
• Bonding energies are relatively small on the order of only 10kJ/mol or
0.1 eV/atom.
• Exists between virtually all atoms or molecules, but its presence may
be obscured if any of the three primary bonding types are present.
76. Secondary, van der Waals, or physical bonds
• Evidenced for the inert gases, which have stable electron structures,
and between molecules that are covalently bonded.
• Normally atomic or molecular dipoles are involved. Dipoles exist
whenever there is some separation of positive and negative portion
of an atom or molecule.
77. Secondary,
van der
Waals, or
physical
bonds
• Bonding results from the coulombic attraction
between the positive end of one dipole and the
negative region of an adjacent one.
• Occur between induced dipoles and polar
molecules (which have permanent dipoles), and
between polar molecules.
78. Hydrogen Bonding
• A special type of secondary bonding.
• A strong secondary interatomic bond that exists between a bound
hydrogen atom (the unscreened proton) and the electrons of
adjacent atoms.
79. Dipoles
• An electric dipole is a separation of positive and negative charges.
• The simplest example of this is a pair of electric charges of equal
magnitude but opposite sign, separated by some (usually small)
distance
80. Fluctuating Induced Dipole Bonds
• A dipole may be created or induced in an atom or molecule that is
normally electrically symmetric.
81. Dipoles
• Fluctuating Symmetric refers to the overall spatial distribution of the
electrons in symmetry with respect to the positively charged nucleus.
Dipole Bonds
• All atoms are experiencing constant vibration that can cause
instantaneous and short lived distortions of electrical symmetry and
can create small electric dipoles.
• These attractive forces may exist between large number of atoms or
molecules, which forces are temporary and fluctuate with time.
82. Polar Molecule-Induced Dipole Bonds
• Polar molecule
• Are molecules in which there exist a permanent electric dipole moment by
virtue of the asymmetrical distribution of positively and negatively charged
regions.
Figure 2.14. Schematic representation of a
polar hydrogen chloride (Hcl) molecule.
83. Permanent Dipole Bonds
• The associated bonding energies are significantly greater than for
bonds involving induced dipoles.
• Also called as electret.
• A special case of polar molecule bonding is the Hydrogen bond.
• Hydrogen bond
• Strongest secondary bonding type
• Examples are HF, H2O and NH3.
• Hydrogen is covalently bonded with fluorine, oxygen and nitrogen.
85. Hydrogen bond
• The single hydrogen electron is shared with the other atom.
• The hydrogen end of the bond is basically a positively charge bare
proton because it is unscreened by any electron.
• This highly positive end is capable of strong attractive force with the
negative end of an adjacent molecule.
• Magnitude is generally greater than that of the other types of
secondary bonds and may be as high as 51kJ/ mol (0.52 eV/molecule)
• Melting and boiling temperatures for hydrogen fluoride and water are
abnormally high in light of their low molecular weights, as a
consequence of hydrogen bonding.
87. Molecules
• Many are composed of groups of atoms that are bound together by
strong covalent bonds.
Examples.
• Elemental diatomic molecules (F2, O2, H2 etc)
• Compounds (H2O, CO2, HNO3, C6H6, CH4 etc)
• Bonds between molecules are weak secondary ones
88. Molecules
• Molecular materials have relatively low melting and boiling
temperatures.
• Small molecules – gases at ordinary, or ambient, temperatures and
pressures
• Large molecules – modern polymers exist as solids, some of the
properties are strongly dependent on the presence of van der waals
and hydrogen secondary bonds.
89. Summary
• Electrons in Atoms
• The two atomic models are Bohr and wave-mechanical. Whereas the Bohr model
assumes electrons to be particles orbiting the nucleus in discrete paths, in wave
mechanics we consider them to be wavelike and treat electron position in terms
of a probability distribution.
• The energies of electrons are quantized—that is, only specific values of energy
are allowed.
• The four electron quantum numbers are n, l, ml, and ms. Each of these specifies a
distinct electron characteristic.
• According to the Pauli exclusion principle, each electron state can accommodate
no more than two electrons, which must have opposite spins.
90. Summary
• The Periodic Table
• Elements in each of the columns (or groups) of the periodic table have distinctive
electron configurations. For example,
• Group 0 elements (the inert gases) have filled electron shells, and Group IA
elements (the alkali metals) have one electron greater than a filled electron
shell.
91. Summary
• Bonding Forces and Energies
• Bonding force and bonding energy are related to one another according to
Equation 2.4.
• Attractive, repulsive, and net energies for two atoms or ions depend on
interatomic separation per the schematic plot.
• From a plot of interatomic separation versus force for two atoms/ions, the
equilibrium separation corresponds to the value at zero force.
• From a plot of interatomic separation versus potential energy for two atoms/ions,
the bonding energy corresponds to the energy value at the minimum of the curve
92. Summary
• Primary Interatomic Bonds
• For ionic bonds, electrically charged ions are formed by the transference of
valence electrons from one atom type to another. This type of bonding is found in
ceramic materials.
• There is a sharing of valence electrons between adjacent atoms when bonding is
covalent. Polymers and some ceramic materials covalently bond.
• The percent ionic character (%IC) of a bond between two elements (A and B)
depends on their electronegativities (X’s).
• With metallic bonding, the valence electrons form a “sea of electrons” that is
uniformly dispersed around the metal ion cores and acts as a form of glue for
them.
• Metallic materials exhibit this type of bonding.
93. Summary
Important Terms and
Concepts
atomic mass unit (amu)
atomic number (Z)
atomic weight (A)
Bohr atomic model
bonding energy
coulombic force
covalent bond
dipole (electric)
electron configuration
electronegative
electron state
electropositive
ground state
hydrogen bond
ionic bond
isotope
metallic bond
mole
Pauli exclusion principle
periodic table
polar molecule
primary bond
quantum mechanics
quantum number
secondary bond
valence electron
van der Waals bond
wave-mechanical model
94. References
Materials Science and Engineering – an Introduction
William D. Callister, Jr. and David G. Rethwisch
• https://depositphotos.com/64489357/stock-illustration-black-and-white-gecko-lizard.html
• https://study.com/academy/lesson/what-is-a-wave-mechanical-model.html
• https://surfguppy.com/ionic-and-covalent-bonding/electronegativity-bond-scale/
• https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplement
al_Modules_(Physical_and_Theoretical_Chemistry)/Physical_Properties_of_Matter/Atomic_and_Molecular_
Properties/Intermolecular_Forces/Specific_Interactions/Lennard-Jones_Potential
• https://biodifferences.com/difference-between-covalent-metallic-and-ionic-bonds.html