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This 39 page Class Notes was uploaded by Lyda Ryan I on Wednesday September 23, 2015. The Class Notes belongs to ENGR220 at Drexel University taught by ChristopherWeyant in Fall. Since its upload, it has received 51 views. For similar materials see /class/212336/engr220-drexel-university in Engineering and Tech at Drexel University.
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Date Created: 09/23/15
Announcements 442012 Read quotBonding in Solids in quotUseful Extra Files on BbVista Week 2 Recitations Chapter 2 problems Quiz 1 Take home quiz to be turned in at the beginning of recitation in Week 3 416 420 Problems 214 and 220 Today s Objectives Structures in solids Atomic structure electron configuration M51 Structures in Solids 2sarhllal NUCIEUS Electron Structure in atoms Atomic bonding is orbital 35 ovbltal AngstromNano level Atomic arrangements in solids Crystalline structures NanoMicron level 17 L Grains 14 Steel Grain Structure Atomic Structure Freshman Chem Atom 911 x 103931 kg 167 x 1027 kg of protons in nucleus of atom of electrons of neutral species A amu 112 mass of 12C weight of 6022 x 1023 molecules or atoms 1 amuatom 1 gmol C 12011 H 1008 M51 Atomic Structure Why in materials do we care about atomic structure Valence electrons determine all of the following properties 1 2 3 4 M51 Electronic Structure in Atoms Quantum mechanics govern atomicsubatomic particle Simple early model of atom was the Bohr model Electrons revolve in Orb ta39e em Only certain energies are allowed Electron changes correspond to quantum jumps to Higher level absorb energy Lower level emit energy M51 Electronic Structure in Atoms Bohr model had limitations because it could not describe various electron phenomena Wavemechanical model developed Orbitals Position defined by of electron at various locations Dmmmmb around nucleus i Uncertain Principle states that both particle O b m39e39m NW gt momentum and position cannot be determined simultaneously Probability 0 Electronic Structure in Atoms Schrodinger s equation defines a 10 that can used to determine the of finding an electron at a certain Probability location l 02w 87r2me g 6x2 hz Etot E10015 O 0 i lt Distance from nucleus E gt Orbital electron Nucleus Electronic Structure in Atoms Electrons have wavelike and particlelike properties Each orbital is described by a discrete energy level defined by Quantum Designation n principal energy levelshell K L M N O 1 23 etc I subsidiary orbitals s p df 0 1 2 3 n1 m magnetic 1 3 5 7 l to I ms spin 12 V2 M51 Pauli s Exclusion Principle No two electrons can have the same quantum numbers This leads to being able to have all the elements of the periodic table M51 Electron Energy States Electrons have discrete 0 tend to occupy available energy state 0 each electron state can accommodate electrons m V2 2 f d f d g f d g l dquot a 1 11 E LJ 1 2 3 4 5 6 7 Principal quantum number n gt Electron Energy States Electron orbitals O 1 2 etc or s p d f Describe probabilistic location of electrons at a certain energy n2 39 i 7 O cccc sed April 3 2012 lthttpchemlinksbeloiteduStarspagesorbilalshtmlgt Electron Energy States Electron orbitals O 1 2 etc or s p d f Describe probabilistic location of electrons at a certain energy 1 39y S X Z Z Z y y y p1 X p0 X p1 X Z Z Z Z Z r d2 X 1 X do X d1 X d2 X Z Z Z Z Z y y y quot y Y 4 y y y x T y 3 X 2 X f1 X to X f1 X f2 X 39 f3 X y 39 L 39 39 39 7 in 39 iorbitalsgt A CCCC sed April 3 2012 SURVEY OF ELEMENTS 0 Most elements Electron configuration Element Atomic Electron configuration Hydrogen 1 15 1 Helium 2 15 2 stable Lithium 3 15 225 1 Beryllium 4 15 2252 Boron 5 15 225 22p 1 Adapted from Table 22 Carbon 6 15 225 22p 2 CalisterampRethwisch 8e Neon 10 15 225 22p 5 stable Sodium 11 1522522p53s1 Magnesium 12 15 225 22p 535 2 Aluminum 13 1522522p53s 23p1 Argon 18 15 225 22p 535 23p 5 stable Krypton 36 15 225 22p 635 23p 53d 10 4s 24p 5 stable 0 Why shell usually not filled completely We Electron Configurations those in unfilled shells Filled shells are more Valence electrons are most available for bonding and tend to control the example C atomic number 6 152 252 2p2 11151 Electronic Configurations Example Featomic 26 132 2322p6 332 3p6 3d6 452 4p Nshell n 4 w 43 1 Energy 1 1 1 M shell n 3 Adapted from Fig 24 Calister amp Rethwisch 8e 35 i 1 Lshell n 2 18 H Kshell n 1 gills The Periodic Table Columns Similar structure 1 U1 QJ CU H 3 0 cu 39m 010 5 N H t 2 a e w D C an m I D Metal U gt 0 IA rquot 1 U 0 T OD Q j Nonmetal 390 39T H quotA 1 IllA IVA VA VIA VIIA He 3 4 i Intermediate 5 6 7 8 1 LI Be B C N O F NE 11 12 13 14 15 16 17 18 vm Ad t df Na Mg MB NB VB v13 VIIB quot I8 1113 Al 5 P 5 CI Air H 33 mm 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 Cg 39 amp K Ca 39 TI V Cr Mn Fe Co Ni Cu Zn Ga Ge As 5e Br KI a Mgr 37 38 39 40 41 42 43 44 45 46 47 4s 49 so 51 52 53 54 RethW SCh 8339 Rb Sr 1 Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te X3 55 56 Rare 72 73 74 75 75 77 78 79 80 81 82 83 84 85 86 C5 Ba 322quot Hf Ta W Re 05 lr Pt Au Hg Tl Pb BI Po At Rn 87 88 m1 104 105 106 107 108 109 110 Fr Ra 3 Rf Db Sg Bh Hs Mt Ds Electropositive elements Electronegative elements Readily give up electrons Readily acquire electrons H to become ions to become ions ll umvERsITv Electronegativity 0 Ranges from 07 to 40 Large values tendency to electrons L L H He 21 HA HA IVA VA VIA VIIA Li Be B C N O F Ne 10 15 20 25 30 35 40 Na Mg VI Al P 5 Cl Al 09 12 lllB VB VB VIB VllB quot lB IIB 15 18 21 25 30 K Ca Sc T1 V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 08 10 13 15 16 16 15 18 18 18 19 16 16 18 20 24 28 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te 1 Xe 08 10 12 14 16 18 19 22 22 22 19 17 17 18 19 21 25 7 Cs Ba LaLu Hf Ta W Re 05 Ir Pt Au Hg 11 Pb Bi Po At Rn 07 09 1142 13 15 17 19 22 22 22 24 19 18 18 19 20 22 Fr Ra AcNo 07 09 11 17 Smaller electronegativity Larger electronegativity Adapted from Fig 27 Calisteramp Rethwisch 8e Fig 27 is adapted from Linus Pauling The Nature of the Chemical Band 3rd edition Copyright 1939 and 1940 3rd edition Copyright 1960 by Cornell University 2 eel Next Time Friday 46 Topic Atomic Bonding in Solids Reading Assignment quotBonding in Solids on BbVista site Chapter 2528 Next Assignment Chapter 2 homework problem set will be discussed in recitation during Week 2 49413 Next Quiz Quiz 1 Takehome quiz Problems 214 amp 220 due at the beginning of Week 3 416420 recitations M151 Announcements 462012 Note Use SI units for this course m 5 kg N Pa etc This Week s Recitations Discussion of Chapter 2 homework problems Quiz 1 Take home quiz to be turned in at the beginning of recitation in week 3 416420 Problems 214 and 220 Today s Objectives Week 3 inclass project rules Atomic arrangement in metals Crystal structures M51 Week 3 Recitations lnClass Group Project Rules for the inrecitation Unit Cell building proiect Each group will build ONE of the following unit cells SC BCC FCC HCP NaCl Diamond CubicZinc Blende ZnS You need to understanddemonstrate the relationship between the following pairs BCC and CsCl Diamond Cubic and ZnS In Week 3 each groupteam will build and present their assigned unit cell There will be 6 groups so each will get ONE unit cell quotPresentquot means explaining to the rest of the class 1 How many atoms per unit cell 2 Which atoms touch and where 3 The relationship between a and r 1151 9 Week 3 Recitations lnClass Group Project Scoringgrading will be based on team voting and recitation instructor ballots that will be given out and collected in Week 3 recitations It will be a simple rating of Aesthetics Accuracy How well each group presents their structure and answers questions Ml i39 Type Ionic Ceramics Covalent Ceramics amp Polymers Metallic Metals Secondary Polymers Last Time Atomic Bonding Bond Energy electron Large Na cation CI anion stable Coulombic stable Attraction Variable largeDiamond smallBismuth Variable largeTungsten smallMercury secondary smallest 48 bondng 90 Last Time Atomic Bonding Why are bond energies positive Table 23 Bonding Energies and Melting Temperatures for Various Substances Bonding Energy Melting eVA tom Temperature Bonding Type Substance kJmol Ion Molecule C Ionic NaCl 640 33 801 MgO 1000 52 2800 Covalent Si 450 47 1410 C diamond 713 74 gt3550 Hg 68 07 39 A1 324 34 660 Metalhc Fe 406 42 1538 i C W 849 88 3410 Ar 77 008 189 Van der Waals C12 31 032 101 NH3 35 036 78 Hydrogen H20 51 052 0 39 quot 39 a H W51 Secondary Bonding Van der Waals forces may be small but that does not mean that they are not useful beyond holding polymers together Crystal Structures How do atoms assemble into solid structures Atomic Arrangements Combination Crystalline amp Amorphous Crystalline Solids Amorphous Solids Long amp Short Range Order Short Range Order Most Polymers amp Inorganic Glasses Metals amp Some Polymers Ceramcs Glasses amp Ceramics Energy and Packing Non dense packing Energy typical neighbor bond length typical neighbor bond energy 39 Dense packing Energy 6 typical neighbor bond energy typical neighbor bond length Dense ordered packed structures tend to have lower energies Materials and Packing materials 0 atoms pack in periodic 3D arrays typical of metals many ceramics some polymers crystalline Si02 Adapted from Fig 3133 0 Calister amp Rethwisch 8e Si 0 Oxygen materials 0 atoms have no periodic packing occurs for compex structures rapid cooling u H Noncrystalline noncrystalline Si02 Adapted from Fig 323b Calister amp Rethwisch 8e M51 Metallic Crystal Structures How can we stack metal atoms to minimize empty space 2dimensions VS Now stack these 2 D layers to make 3D structures 11115 Metallic Crystal Structures Tend to be packed Reasons for packing Typically only one element is present so all atomic radii are Metallic bonding is not Nearest neighbor distances tend to be small in order to bond energy Electron cloud shields cores from each other 0 Have the simplest crystal structures We will examine three such structures M51 Metallic Crystal Structures Unit Cells Small repeat units which describe the crystalline structure of a solid These identical quotunit cells extend in all directions In two dimensions l One unit cell WT Metallic Crystal Structures Unit Cells Small repeat units which describe the crystalline structure of a solid These identical quotunit cells extend in all directions In two dimensions One unit cell M151 Metallic Crystal Structures Unit Cells Small repeat units which describe the crystalline structure of a solid These identical quotunit cells extend in all directions In two dimensions quot quotquot 0 x a I I I G One unit cell M51 Metallic Crystal Structures 3D Unit Cells Atoms in crystals are of course arranged in three dimensional unit cells One unit cell M51 Metallic Crystal Structures 3D Unit Cells Atoms in crystals are of course arranged in three dimensional unit cells Four three dimension arrangements found in metals SC Simple Cubic BCC BodyCentered Cubic FCC FaceCentered Cubic HCP Hexagonal ClosePacked M51 Simple Cubic Structure SC 0 Rare due to low packing density only Po has this structure 0 are cube edges 0 Coordination 6 nearest neighbors Atomic Packing Factor APF Volume of atoms in unit cell APF Volume of unIt cell assume hard spheres APF for a simple cubic structure 052 volume I atoms i atom unit cell 1 w m quot r Q Al R050 APF a3v volume closepacked directions contains 8 x 18 1 atomunit cell Adapted from Fig 324 M I Body Centered Cubic Structure BCC Atoms touch each other Note All atoms are identical the center atom is shaded differently only for ease of viewing ex Cr W Fe 0c Tantalum Molybdenum 0 Coordination 8 A Adapted from Fig 32 Calister amp Rethwisch 8e Courtesy PM Anderson 2 atomsunit cell 1 center 8 corners x 18 M1151 Atomic Packing Factor BCC 0 APF for a bodycentered cubic structure 068 J a Closepacked directions g za rmamp a 39ength M 5quot Rethwisch 8e l atoms unhce APF volume 561 unit cell M151 Next Time Wednesday 411 Topic Packing in Crystals Reading Assignment Chapter 312314 Next Assignment Chapter 2 homework problem set will be discussed in recitation this week 49 413 Next Quiz Quiz 1 Takehome quiz Problems 214 amp 220 due at the beginning of Week 3 416 420 recitations Midterm Exam 1 Tuesday 424 800850 am in Main Auditorium M151
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