Introduction To Materials PDF

Introduction to Materials Introduction to Material Science Fundamentals: Atomic Structure, Bonds and Classes of Materials Reto Luginbuehl, Blaser Swisslube, 3415 Hasle-Rüegsau 1 Chapter 2: Atomic Structure & Interatomic Bonding Aims 2 • The structure of atoms • What characteristics of ato...

Introduction to Materials Introduction to Material Science Fundamentals: Atomic Structure, Bonds and Classes of Materials Reto Luginbuehl, Blaser Swisslube, 3415 Hasle-Rüegsau 1 Chapter 2: Atomic Structure & Interatomic Bonding Aims 2 • The structure of atoms • What characteristics of atoms/molecules promote interatomic/intermolecular bonding • What types of interatomic/intermolecular bonds exist ? • What properties of materials depend on the magnitude of interatomic/intermolecular bonds? • What material classes exist? Fundamentals: Atomic Structure and Bonds 2 week 01: atomic structure and classes of materials Page 1 Introduction to Materials State of Aggregation • States of Matter (Ancient View): Earth, Water, Wind, Fire • States of Matter (Modern View) Solid 3 Liquid Gas Plasma Fundamentals: Atomic Structure and Bonds 3 State of Aggregation different states and transitions gas liquid solid 4 Fundamentals: Atomic Structure and Bonds 4 week 01: atomic structure and classes of materials Page 2 Introduction to Materials State of Aggregation different states and transitions Plasma Enthalpy is a measure of the total energy of a thermodynamic system H(S,p)=U+pV 5 Fundamentals: Atomic Structure and Bonds 5 The Elements Change of state by increased enthalpy 6 Fundamentals: Atomic Structure and Bonds 6 week 01: atomic structure and classes of materials Page 3 Introduction to Materials State of Aggregation different states – different behavior Volume 7 Fundamentals: Atomic Structure and Bonds 7 The Atom 8 Fundamentals: Atomic Structure and Bonds 8 week 01: atomic structure and classes of materials Page 4 Introduction to Materials Material Properties Three times Aluminum Oxide: what is the difference? Transparent versus translucent versus opaque It’s the aim that you understand some of the fundamental behind that phenomena! 9 Fundamentals: Atomic Structure and Bonds 9 Material Properties Material Classes: Why are metals more dens that other material classes? It’s the aim that you understand some of the fundamental behind that phenomena! 10 Fundamentals: Atomic Structure and Bonds 10 week 01: atomic structure and classes of materials Page 5 Introduction to Materials Material Properties Material Classes: Why do metal exhibit a similar stiffness as ceramics? It’s the aim that you understand some of the fundamental behind that phenomena! 11 Fundamentals: Atomic Structure and Bonds 11 Material Properties Material Classes: Why do metal exhibit a higher fracture toughness as compared to ceramics or polymers? It’s the aim that you understand some of the fundamental behind that phenomena! 12 Fundamentals: Atomic Structure and Bonds 12 week 01: atomic structure and classes of materials Page 6 Introduction to Materials The Atom The two most important identifiers of an atom are: • its mass • its electronic structure Some properties are determined by an atom's structure: • Chemical • Electrical • Thermal • Optical • Magnetic 13 Fundamentals: Atomic Structure and Bonds 13 The Atom The two most important identifiers of an atom are: 14 • its mass • its electronic structure Dimension: Masses: Charge: Electron < 10-19 m 9.1×10−31 kg -1.6x10-19C Proton 0.87 fm 1.6×10−27 kg +1.6x10-19C Neutron 0.87 fm 1.6×10−27 kg 0 Nucleus 1-10 fm Variable* Atom  0.1 nm = 1 Å 1.6×10−27 variable* to 4.5×10−25 kg variable* Fundamentals: Atomic Structure and Bonds 14 week 01: atomic structure and classes of materials Page 7 Introduction to Materials The Atom The two most important identifiers of an atom are: • its mass • its electronic structure atomic number = # of protons in nucleus of atom atomic mass unit = amu = 1/12 mass of 12C atomic mass and mol mass = wt of 6.022 x 1023 molecules or atoms 1 amu/atom = 1 g/mol 15 = # of electrons in neutral species C 12.011 H 1.008 Fundamentals: Atomic Structure and Bonds 15 The Mass of Atoms The Atomic Number of the Elements 16 Fundamentals: Atomic Structure and Bonds 16 week 01: atomic structure and classes of materials Page 8 Introduction to Materials The Mass of Atoms  While the number of protons defines the element, the number of neutrons may vary! Element Hydrogen, H Atomic Protons number 1 1 Helium, He 2 2 Lead, Pb 82 82 Neutrons abundance 0 1 2 99.99 % 0.01 % 100.0 % 122 124 125 126 1.4 % 24.1 % 22.1 % 52.4 % average molar mass 1.008 4.003 207.19  Elements that differ in their number of neutrons are called isotopes 17 Fundamentals: Atomic Structure and Bonds 17 The Electronic Structure of Atoms 18 • Electrons have wavelike and particulate properties. • The electrons are bound by Coulomb attraction to the positively charge nucleus • Two of the wavelike characteristics are • electrons are in orbitals defined by a probability. • each orbital at discrete energy level is determined by quantum numbers. • Quantum # n = principal (energy level-shell) = subsidiary (orbitals) l ml = magnetic Designation K, L, M, N, O (1, 2, 3, etc.) s, p, d, f (0, 1, 2, 3,…, n-1) 1, 3, 5, 7 (- to + )l l ms = spin ½, -½ Fundamentals: Atomic Structure and Bonds 18 week 01: atomic structure and classes of materials Page 9 Introduction to Materials The Electronic Structure of Atoms n= 4 n= 3 n= 2 N M L n= 1 K 19 • All electrons are localized around the nucleus in discrete shells • The binding energy of an electron is the work required to remove the electron from the atom Fundamentals: Atomic Structure and Bonds 19 The Electronic Structure of the Atom • The negatively charged electrons are "associated" with the positively charged nucleus as electron cloud in three dimensional resonant standing waves. • The modes of resonance for single electron systems such as the hydrogen atom are described by the Schrödinger wave equation: • Solutions to the Schrödinger wave equation correspond to modes of electron resonance and are formally called wave functions. • Although not exactly the same, chemists tend to call wave functions "orbitals”. • Heisenberg uncertainty principle: “There is a fundamental limit to just how precisely we can measure both the position and the momentum of a particle at the same time.”  An orbital is the space that describe the most probable location of the electrons around the nucleus www.meta-synthesis.com 20 Fundamentals: Atomic Structure and Bonds 20 week 01: atomic structure and classes of materials Page 10 Introduction to Materials The Electronic Structure of Atoms The Orbital Graphics from wikibooks.org 21 Fundamentals: Atomic Structure and Bonds 21 The Electronic Structure of Atoms • The quantification leads to specific symmetries of the atomic orbitals • There are s, p, d, and f orbitals • s-orbitals are spherical and each shell has an s-orbital Graphics from wikibooks.org 22 Fundamentals: Atomic Structure and Bonds 22 week 01: atomic structure and classes of materials Page 11 Introduction to Materials The Electronic Structure of Atoms • p-orbitals have two charged elliptical areas/lobes which are oriented along the axis of xyz coordinate system. There are 3 types of p-orbital shapes: Graphics from wikibooks.org 23 Fundamentals: Atomic Structure and Bonds 23 The Electronic Structure of Atoms • d-orbitals have four charged lobes and 5 d-orbitals shapes • f-orbitals have six charged lobes and 7 f-orbital shapes exist Graphics from wikibooks.org 24 Fundamentals: Atomic Structure and Bonds 24 week 01: atomic structure and classes of materials Page 12 Introduction to Materials The Electronic Structure of Atoms • Each shell has a specific number of orbitals • Each orbital can be occupied by only two electrons • The Pauli Exclusion principle states that no two electrons can exist in the same place with the same set of quantum number Orbitals Number of electrons per shell n= 4 n= 3 n= 2 N M L 4s, 4p, 4d, 4f 3s, 3p, 3d 2s, 2p 32 18 8 n= 1 K 1s 2 26 Fundamentals: Atomic Structure and Bonds 26 Electronic Configurations 4d 4p N-shell n = 4 3d 4s Energy 27 3p 3s M-shell n = 3 2p 2s L-shell n = 2 1s K-shell n = 1 Fundamentals: Atomic Structure and Bonds 27 week 01: atomic structure and classes of materials Page 13 Introduction to Materials The Mass of Atoms The Atomic Number of the Elements 28 Fundamentals: Atomic Structure and Bonds 28 Electronic Configurations of Elements Element Hydrogen Helium Lithium Beryllium Boron Carbon ... Atomic # 1 2 3 4 5 6 Electron configuration 1s 1 1s 2 (stable) 1s 2 2s 1 1s 2 2s 2 1s 2 2s 2 2p 1 1s 2 2s 2 2p 2 ... Neon Sodium Magnesium Aluminum ... 10 11 12 13 1s 2 2s 2 2p 6 (stable) 1s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 3s 2 1s 2 2s 2 2p 6 3s 2 3p 1 ... Argon ... Krypton 18 ... 36 1s 2 2s 2 2p 6 3s 2 3p 6 (stable) ... 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 (stable) For most elements: The Electron configuration is not stable! 29 Fundamentals: Atomic Structure and Bonds 29 week 01: atomic structure and classes of materials Page 14 Introduction to Materials Electronic Configurations of Elements • • • Valence electrons – those in unfilled shells Filled shells are more stable Valence electrons are most available for bonding and tend to control the chemical properties • example: C (atomic number = 6) 1s2 2s2 2p2 valence electrons 30 Fundamentals: Atomic Structure and Bonds 30 Electronic Configurations of Elements ex: Fe - atomic # = 26 1s2 2s2 2p6 3s2 3p6 3d 6 4s2 4d 4p N-shell n = 4 valence electrons 3d 4s Energy 31 3p 3s M-shell n = 3 2p 2s L-shell n = 2 1s K-shell n = 1 Fundamentals: Atomic Structure and Bonds 31 week 01: atomic structure and classes of materials Page 15 Introduction to Materials The Electronic Structure of the Atom • Strongest binding energy levels always fill first • Maximum two electrons per orbital www.meta-synthesis.com 32 Fundamentals: Atomic Structure and Bonds 32 The Electronic Structure of the Atom 33 • The lowest binding energies is found in the largest orbitals  these electrons are call valence electrons • The strongest binding energies is found close to core  these electrons are call core electrons • The higher the atomic number, the higher the binding energies of core electron Fundamentals: Atomic Structure and Bonds 33 week 01: atomic structure and classes of materials Page 16 Introduction to Materials Historical Perspective Antoine Laurent de Lavoisier (1743-1794) is considered to be one of the fathers of modern chemistry. In its textbook Traité Élémentaire de Chimie (Elementary Treatise of Chemistry), he describes a list of "simple substances" that Lavoisier believed could not be broken down further, among some elements the list included also 'light' and 'caloric', which at the time were believed to be material substances. He predicted the existence of silicon which was not known at the time. 34 Fundamentals: Atomic Structure and Bonds 34 Historical Perspective Alexandre-Émile Béguyer de Chancourtois (1820 –1886) was a French geologist and mineralogist who was the first to arrange the chemical elements in order of atomic weights, doing so in 1862. De Chancourtois only published his paper, but did not publish his actual graph with the proposed arrangement. 35 Fundamentals: Atomic Structure and Bonds 35 week 01: atomic structure and classes of materials Page 17 Introduction to Materials Historical Perspective Dmitri Ivanovich Mendeleev (1834 –1907) was a Russian chemist and inventor. He formulated the Periodic Law, created his own version of the periodic table of elements, and used it to correct the properties of some already discovered elements and in addition, to predict the properties of eight elements yet to be discovered. 36 Fundamentals: Atomic Structure and Bonds 36 Today: Periodic Table of Elements https://en.wikipedia.org 37 • Mendeleyev grouped and introduced what is today called the periodic table of elements • The elements are grouped according to the quantum number and occupied orbitals • Elements with a similar electron configuration exhibit a similar chemical behavior Fundamentals: Atomic Structure and Bonds 37 week 01: atomic structure and classes of materials Page 18 Introduction to Materials The Periodic Table give up 1egive up 2egive up 3e- accept 2eaccept 1einert gases • Columns: Similar Valence Structure H Li He Be O Na Mg K Ca Sc Rb Sr Y F Ne S Cl Ar Se Br Kr I Xe Te Cs Ba Po At Rn Fr Ra Electropositive elements: Readily give up electrons to become + ions. 38 Electronegative elements: Readily acquire electrons to become - ions. Fundamentals: Atomic Structure and Bonds 38 Electronic Configurations of Elements Element Hydrogen Helium Lithium Beryllium Boron Carbon ... Atomic # 1 2 3 4 5 6 Electron configuration 1s 1 1s 2 (stable) 1s 2 2s 1 1s 2 2s 2 1s 2 2s 2 2p 1 1s 2 2s 2 2p 2 ... Neon Sodium Magnesium Aluminum ... 10 11 12 13 1s 2 2s 2 2p 6 (stable) 1s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 3s 2 1s 2 2s 2 2p 6 3s 2 3p 1 ... Argon ... Krypton 18 ... 36 1s 2 2s 2 2p 6 3s 2 3p 6 (stable) ... 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 (stable) For most elements: The Electron configuration is not stable! 39 Fundamentals: Atomic Structure and Bonds 39 week 01: atomic structure and classes of materials Page 19 Introduction to Materials Electronegativity • Ranges from 0.7 to 4.0, • Large values: tendency to acquire electrons. Smaller electronegativity 40 Larger electronegativity Fundamentals: Atomic Structure and Bonds 40 41 Na Mg K Ca Rb Sr Cs Ba Fr Ra inert gases accept 1e- Be accept 2e- H Li O F Ne S Cl Ar Sc Se Br Kr Y Te I Xe Po At Rn give up 3e- give up 1e- give up 2e- The Periodic Table He giving up electrons is called accepting electrons is called oxidation reduction Fundamentals: Atomic Structure and Bonds 41 week 01: atomic structure and classes of materials Page 20 Introduction to Materials Electronegativity Electronegativity is a parameter that can be used to predicting chemical structure and reactivity electronegativity is an atomic property that is conserved in molecules and ionic substances: • The electronegative elements, found top-right, present as non-metals. Fluorine, F2, oxygen, O2, & chlorine, Cl2, are strong oxidizing agents: they accept electrons and are easily reduced. • The electropositive elements all present as metals. Metals behave as electron donating reducing agents. Metals form cations that behave as Lewis acids. 42 Fundamentals: Atomic Structure and Bonds 42 The Electronic Structure • The following properties are determined by electronic structure 1) 2) 3) 4) 43 Chemical Electrical Thermal Optical Fundamentals: Atomic Structure and Bonds 43 week 01: atomic structure and classes of materials Page 21 Introduction to Materials Materials Groups Types of Bonds: There are three major types of bonds Ionic Bonding Metallic Bonding Covalent Bonding 44 Fundamentals: Atomic Structure and Bonds 44 Type of Bonds in Solid Materials ionic metallic 45 covalent Fundamentals: Atomic Structure and Bonds 45 week 01: atomic structure and classes of materials Page 22 Introduction to Materials From Atoms to Molecules Hydrogen: 47 Fundamentals: Atomic Structure and Bonds 47 From Atoms to Molecules Hydrogen: Covalent bonds are formed if one or more pairs of electrons are shared by two atoms 48 Fundamentals: Atomic Structure and Bonds 48 week 01: atomic structure and classes of materials Page 23 Introduction to Materials give up 1egive up 2egive up 3e- accept 2eaccept 1einert gases The Periodic Table increasing reactivity H Li pure elements like H, N, O, F, Cl, Br, I are only stable when forming dimers H2, N2, O2, F2, Cl2, Br2, I2 He Be O Na Mg F Ne Ar S Cl Ca Sc Se Br Kr Rb Sr Y Te I Xe K For most elements: the Electron configuration is not stable! Cs Ba Po At Rn all other elements react or form some kind of bonds Fr Ra 49 Fundamentals: Atomic Structure and Bonds 49 Covalent Bonding • similar electronegativity  share electrons • bonds determined by valence – s & p orbitals dominate bonding • Example: Methane, CH4 C: has 4 valence e-, CH4 H shared electrons from carbon atom needs 4 more H: has 1 valence e-, H C needs 1 more Electronegativities H are comparable. H shared electrons from hydrogen atoms More on structure relationship of covalent bonding in the chapter on polymers 50 Fundamentals: Atomic Structure and Bonds 50 week 01: atomic structure and classes of materials Page 24 Introduction to Materials Ionic Bonding • Occurs between cations (+) and anions (-) • Requires electron transfer • Large difference in electronegativity required • Example: NaCl Na (metal) unstable Cl (nonmetal) unstable electron Na (cation) stable 51 - + Coulombic Attraction Cl (anion) stable Fundamentals: Atomic Structure and Bonds 51 Ionic Bonding Ionic bonds are formed if one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other 52 Fundamentals: Atomic Structure and Bonds 52 week 01: atomic structure and classes of materials Page 25 Introduction to Materials Ionic Bonding • Energy – minimum energy most stable • Energy balance of attractive and repulsive terms EN = EA + ER = - A r + B rn Repulsive energy ER Interatomic separation r Net energy EN Attractive energy EA 53 Fundamentals: Atomic Structure and Bonds 53 The Periodic Table of Elements 54 Fundamentals: Atomic Structure and Bonds 54 week 01: atomic structure and classes of materials Page 26 accept 2eaccept 1einert gases Ionic Bonding give up 1egive up 2egive up 3e- Introduction to Materials K Ca Sc Se Br Kr H Ionic bond: metal donates electrons Li Be + Na Mg Rb Sr Y Cs Ba Fr Ra He O F Ne nonmetal S Cl Ar accepts electrons Te I Xe Po At Rn Dissimilar electronegativities ex: MgO Mg 1s2 2s2 2p6 3s2 [Ne] 3s2 O 1s2 2s2 2p4 Mg2+ 1s2 2s2 2p6 [Ne] O2- 1s2 2s2 2p6 [Ne] 55 Fundamentals: Atomic Structure and Bonds 55 Ionic Bonding • Predominant bonding in Ceramics NaCl MgO CaF 2 CsCl Give up electrons 56 Acquire electrons Fundamentals: Atomic Structure and Bonds 56 week 01: atomic structure and classes of materials Page 27 Introduction to Materials Ionic Bonding: Composition of Ceramic Materials Ceramic materials are a composed of metals and non-metals atoms Binary composition • NaCl, CsCl, CaF2 “Complex Composition” • Calcium sulphate (CaSO4) • Granit (Aluminosilicate containing Na, K, Ca) • mica (pure aluminosilicate) • Porcelain (K2O-SiO2-Al2O3) Carbon: • Diamond • Graphite • Fullerene Oxides: • Silica (SiO2) • Alumina (Al2O3) • Zirconia (ZrO2) • Titanium dioxide (TiO2) Carbides: • Silicon carbide (SiC) • Tungsten Carbide (WC) • Titanium carbide (TiC) Nitrides: • Silicon nitride (Si3N4) • Titanium nitride (TiN) Boride: • Titanium boride (TiB) More on structure relationship of ionic bonding in the chapter on ceramic materials 57 Fundamentals: Atomic Structure and Bonds 57 Metals in the Periodic Table H Li He Be O Na Mg F Ne Ar S Cl Ca Sc Se Br Kr Rb Sr Y Te I Xe K Cs Ba Po At Rn Fr Ra 58 Fundamentals: Atomic Structure and Bonds 58 week 01: atomic structure and classes of materials Page 28 Introduction to Materials Metallic Bonds: Electronic Structure of Solids Electrons delocalized to form an “electron cloud” 59 Fundamentals: Atomic Structure and Bonds 59 Metallic Bonds: Electronic Structure of Solids 60 • The properties of the electrons in the bonding orbital can be described as the state they are in • The energy level of the state is typically lower than that of the separate atoms • In metals valence electrons are shared among all atoms Fundamentals: Atomic Structure and Bonds 60 week 01: atomic structure and classes of materials Page 29 Introduction to Materials Metallic Bonds: Electronic Structure of Solids • Based on the Pauli exclusion principle all energies of the state must differ  for solids the states form a quasi continuous energy band 61 Fundamentals: Atomic Structure and Bonds 61 Metallic Bonds: Electronic Structure of Solids 62 • Partially filled energy bands of the valence electrons leads to conducting material • When all levels of the valence band are occupied by electrons, the solid has the properties of a ceramic or a polymer Fundamentals: Atomic Structure and Bonds 62 week 01: atomic structure and classes of materials Page 30 Introduction to Materials Types of Primary Bonds Bonds are formed if two atoms are close enough for their atomic orbitals to interact If the electronegativity values of the two atoms is similar very different If the atom are classified as Ionic Bonding non-metals Metallic Bonding If the electronegativity values are 63 similar different Non-Polar Covalent Bonding Polar Covalent Bonding Covalent Bonding metals Fundamentals: Atomic Structure and Bonds 63 Secondary Bonding or Van der Waals Bonding Arises from attractive forces between dipoles • Fluctuating dipoles ex: liquid H H2 asymmetric electron clouds + - + secondary bonding - H H 2 H2 H H secondary bonding • Permanent dipoles -general case: + - secondary bonding + - -ex: liquid HCl H Cl secondary bonding H Cl -ex: polymer 64 linear polymer molecule Fundamentals: Atomic Structure and Bonds 64 week 01: atomic structure and classes of materials Page 31 Introduction to Materials Properties Related to Bonding I: Melting Temperature (Tm) • Bond length, r • Melting Temperature, Tm Energy r • Bond energy, Eo ro Energy r smaller Tm unstretched length ro larger Tm r Eo = The larger Eo, the higher Tm “bond energy” 65 Fundamentals: Atomic Structure and Bonds 65 Properties Related to Bonding II: Coefficient of Thermal Expansion (αl) • Coefficient of thermal expansion, αl length, L o unheated, T 1 ΔL Lo ΔL = αl (T 2 -T 1) heated, T 2 The smaller Eo, the larger αl. non-stretched length Energy ro Eo Eo 66 r larger αl smaller αl • Increase in bond length is due to asymmetry of the E vs. r curve. This results in an increase in al. • As E0 increases this asymmetry decreases. Fundamentals: Atomic Structure and Bonds 66 week 01: atomic structure and classes of materials Page 32 Introduction to Materials Summary: Properties Related to Bonding Type and Bonding Energy Ceramics (Ionic & covalent bonding): Metals (Metallic bonding): Polymers (Covalent & Secondary): 67 Large bond energy high Tm large E small αl Variable bond energy moderate Tm moderate E moderate αl Weak bond energy (between chains) Secondary bonding responsible for most physical properties low Tm small E large αl Fundamentals: Atomic Structure and Bonds 67 Forces between Atoms www.chem.ufl.edu 68 Fundamentals: Atomic Structure and Bonds 68 week 01: atomic structure and classes of materials Page 33 Introduction to Materials Properties of Materials metallic 69 ionic covalent Fundamentals: Atomic Structure and Bonds 69 Summary 70 • A material’s chemical, electrical, thermal, and optical properties are determined by electronic configuration. • Valence electrons occupy the outermost unfilled electron shell. • Primary bonding types include covalent, ionic, and metallic bonding. • Secondary or van der Waals bonds are weaker than the primary bonding types. • All the analytical properties depend on the electronic structure and the mass of atoms and molecules Fundamentals: Atomic Structure and Bonds 70 week 01: atomic structure and classes of materials Page 34 Introduction to Materials 71 Fundamentals: Atomic Structure and Bonds 71 Structure of Solid Materials Crystalline Solid: • Regular repeating units on atomic or molecular level • Any material can form a crystalline arrangements – it is just a question how to transform it Amorphous Solid: • Lack of long-range structural order Regular repeating units on atomic or molecular level due to restrictions in atomic or molecular movement and organization • • 80 Any material can form an amorphous solid A glass is a morpohous solid that can tranform into a liquid upon heating above the glass transition Fundamentals: Atomic Structure and Bonds 80 week 01: atomic structure and classes of materials Page 35