Copyright©2000 by Houghton Mifflin Company. All rights reserved. 1 Chemistry FIFTH EDITION Chapter 10 Liquids and Solids

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 2 Section 10.3 Structure & Types of Solids Crystalline Solids: highly regular arrangement of their components [table salt (NaCl), pyrite (FeS 2 )]. Amorphous solids: considerable disorder in their structures (glass).

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 3 Representation of Components in a Crystalline Solid Lattice: A 3-dimensional system of points designating the centers of components (atoms, ions, or molecules) that make up the substance.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 4 Unit Cell Smallest repeating unit of the lattice. Entire Structure obtained by repeating the unit cell in all 3 dimensions.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 5 Representation of Components in a Crystalline Solid Unit Cell: The smallest repeating unit of the lattice. Three common types: 4 simple cubic 4 body-centered cubic 4 face-centered cubic

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 6 Figure 10.9 Three Cubic Unit Cells and the Correspond ing Lattices

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 7 X-RAY ANALYSIS OF SOLIDS X-RAY DIFFRACTION IS COMMONLY USED TO DETERMINE THE STRUCTURE OF CRYSTALLINE SOLIDS

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 8 DIFFRACTION: SCATTERING OF LIGHT FROM A REGULAR ARRAY OF POINTS IN WHICH THE SPACINGS BETWEEN THE COMPONENTS ARE COMPATIBLE WITH THE WAVELENGTH OF LIGHT

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 9 X-RAYS ARE USED BECAUSE THEIR WAVELENGTHS ARE SIMILAR TO THE DISTANCES BETWEEN ATOMIC NUCLEI

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 10 Figure Page 460 Interference of Light Rays

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 11 Resulting Wave after reflection Depends on the distance the waves travel after reflection.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 12 Figure Diagram to Support the Bragg Equation

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 13 X-ray waves strike two different atoms. Waves will still be in phase and will reinforce each other If The difference in distance traveled after reflection is an integral number of wavelengths.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 14 That is, XY + YZ = n where n = 1,2,3…

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 15 If XY + YZ = n where n = 1,2,3… Then XY + YZ = 2d sin(  ) BRAGG EQUATION: n = 2d sin(  ) d = distance between  = angle of incidence & reflection

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 16 PROBLEM THE SECOND ORDER REFLECTION (n = 2) FOR A GOLD CRYSTAL HAS AN ANGLE OF 22.22° FOR X-RAYS OF 154 pm. WHAT IS THE SPACING (IN BETWEEN THESE CRYSTAL PLANES? 4.08 ÅHomework !!!!

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 17 Types of Crystalline Solids Ionic Solid: contains ions at the points of the lattice that describe the structure of the solid (NaCl). Molecular Solid: discrete covalently bonded molecules at each of its lattice points (sucrose, ice).

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 18 Types of Crystalline Solids Atomic Solid: contains atoms at the points of the lattice that describe the structure of the solid (only one type of atom – diamond, graphite).

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 19 Figure Examples of Three Types of Crystalline Solids

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 20 ATOMIC SOLIDS – 3 Subgroups METALLIC SOLIDS: DELOCALIZED NON-DIRECTIONAL COVALENT BONDING NETWORK SOLIDS: ATOMS BONDED WITH STRONG DIRECTIONAL COVALENT BONDS LEAD TO GIANT MOLECULES OR NETWORKS OF ATOMS GROUP 8A SOLIDS: NOBLE GAS ATOMS ATTRACTED TO EACH OTHER WITH LONDON DISPERSION FORCES

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 21 Section 10.4 Structure & Bonding in Metals METALLIC CRYSTAL --CLOSEST PACKING MODEL --METAL ATOMS ASSUMED TO BE UNIFORM HARD SPHERES PACKED TO BEST UTILIZE THE AVAILABLE SPACE --MOST EFFICIENT USE OF SPACE

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 22 TWO TYPES 1)HEXAGONAL CLOSEST PACKED (hcp) STRUCTURE -- aba PACKING -- 2 ND LAYER LIKE THE 1 ST LAYER BUT WITH SPHERES IN DIMPLES OF 1 ST LAYER -- 3 RD LAYER HAS ATOMS DIRECTLY OVER ATOMS OF 1 ST LAYER

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 23 Figure The Closest Packing Arrange ment of Uniform Spheres

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 24 Figure Hexagonal Closest Packing

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 25 CUBIC CLOSEST PACKED (ccp) Structure -- abc PACKING -- 3 RD LAYER IN DIMPLES OF 2 ND LAYER BUT NO SPHERES LIE DIRECTLY ABOVE 1 ST LAYER -- 4 TH LAYER IS LIKE 1 ST LAYER

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 26 Figure The Closest Packing Arrange ment of Uniform Spheres

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 27 Figure Cubic Closest Packing

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 28 Unit Cell of Cubic Closest Packed Structure is the same arrangement As Face-Centered Cubic Unit Cell.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 29 Figure For both hcp & ccp, the Indicated Sphere Has 12 Nearest Neighbors

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 30 COORDINATION NUMBER NUMBER OF NEAREST NEIGHBORS IN hcp & ccp, COORDINATION # IS 12

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 31 SPACE OCCUPIED IN HEXAGONAL CLOSEST PACKED & CUBIC CLOSEST PACKED: SPHERES OCCUPY 74% OF THE SPACE OF THE CRYSTAL

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 32 EXCEPTION: BODY-CENTERED CUBIC STRUCTURE (bcc) -- SPHERES NOT CLOSEST PACKED -- EACH SPHERE HAS ONLY 8 NEAREST NEIGHBORS -- CORDINATION # IS 8, 68% OF SPACE OCCUPIED -- OCCURS FOR Fe & ALKALI METALS -- NOT SURE WHY THIS STRUCTURE IS ADOPTED

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 33 CALCULATING THE DENSITY OF A CUBIC CLOSEST PACKED (Face-Centered Cubic) SOLID

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 34 Figure The Net Number of Spheres in a Face- Centered Cubic Unit Cell

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 35 FACE CENTERED CUBIC CELL ONE-EIGHTH SPHERE ON EACH OF THE 8 CORNERS ONE-HALF SPHERE ON EACH OF THE 6 FACES TOTAL 4 SPHERES PER UNIT CELL

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 36 Sample Exercise 10.2 Read on page Practice

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 37 BONDING MODELS FOR METALS METALS: MALLEABLE DUCTILE CONDUCT HEAT & ELECTRICITY HIGH MELTING POINTS DURABLE BONDING STRONG AND NON-DIRECTIONAL Although it is difficult to separate metal atoms, it is relatively easy to move them, provided the atoms stay in contact with each other.

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 38 ELECTRON SEA MODEL: REGULAR ARRAY OF METAL CATIONS IN A “SEA” OF VALENCE ELECTRONS

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 39 Figure The Electron Sea Model for Metals Postulates a Regular Array of Cations in a “Sea” of Valence Electrons

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 40 Figure The Molecular Orbital Energy Levels Produced When Various Numbers of Atomic Orbitals Interact Another Model

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 41 Figure Let’s Read p. 467 The Band Model for Magnesium

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 42 METAL ALLOYS --- SUBSTANCE THAT CONTAINS A MIXTURE OF ELEMENTS AND HAS METALLIC PROPERTIES

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 43 TWO TYPES OF METAL ALLOYS 1) SUBSTITUTIONAL ALLOY: SOME OF THE HOST METAL ATOMS ARE REPLACED BY OTHER METAL ATOMS OF SIMILAR SIZE EXAMPLES: BRASS, STERLING SILVER, PEWTER

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 44 Figure Two Types of Alloys Substitutional Alloy: Brass 

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 45 INTERSTITIAL ALLOYS -- FORMED WHEN SOME OF THE INTERSTICES (HOLES) IN THE CLOSEST PACKED STRUCTURE ARE OCCUPIED BY SMALL ATOMS EXAMPLE: STEEL, CARBON IN THE HOLES OF IRON CRYSTAL

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 46 Figure Two Types of Alloys Interstitial Alloy: Steel 

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 47 STEEL MILD STEEL: < 0.2% CARBON (NAILS) MEDIUM STEEL: 0.2 – 0.6 CARBON (RAILS, STEEL BEAMS) HIGH-CARBON STEEL: 0.6 – 1.5% CARBON (TOOLS, CUTLERY)

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 48 ALLOY STEELS OTHER ELEMENTS ADDED IN ADDITION TO IRON AND CARBON MIXTURE OF INTERSTITIAL (CARBON) & SUBSTITUTIONAL (OTHER METALS) ALLOY

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 49 Mixtures of interstitial (carbon) & Substitutional (other metal) alloys Used in Expensive Racing Bikes. See Table 10.4 page 470. Homework!

Copyright©2000 by Houghton Mifflin Company. All rights reserved. 50 Section 10.3 STRUCTURE & TYPES OF SOLIDS (1)CRYSTALLINE SOLIDS: Those with highly regular arrangement of their components. (2) AMORPHOUS SOLIDS: Those with considerable disorder in their structures (i.e., glass).