IUB CHEM-C 118 - 10-22 chapter 11 (19 pages)

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10-22 chapter 11



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10-22 chapter 11

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Pages:
19
School:
Indiana University, Bloomington
Course:
Chem-C 118 - Principles of Chemistry and Biochemistry Ii
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Clicker Question Which statement is false A Amorphous solids have very little long range order B Metallic solids are good conductors of heat and electricity C Molecular solids are held together by covalent bonds molecules have covalent bonds molecular solids aren t held together by covalent bonds D Network solids are bonded together into infinite molecules by covalent bonds 11 Solids and Materials 11 5 Types of Solids 11 6 Crystalline Solids 11 7 Network Solids 11 8 Materials Science 11 9 Metals Semiconductors and Insulators 11 10 Silicon and the Chip 11 11 Cement Ceramics and Glass Friday Friday October October 17 17 2014 2014 Read Read Sections Sections 11 5 11 5 for for Friday Friday Sections Sections 11 6 11 6 11 7 11 7 and and 11 8 11 8 for for Wednesday Wednesday End End of of Chapter Chapter 11 11 Problems Problems 59 59 61 61 63 63 65 65 72 72 75 75 77 77 84 84 86 86 88 88 90 90 92 92 93 93 108 108 Types of Solids Solids can be divided into Crystalline solids long range order sharp melting points Amorphous solids no regular repeating units melt over a range of T 11 6 Crystalline Solids Crystals have planar faces and sharp angles The angles are characteristic of the substance they don t depend on crystal size they reflect the shape of the crystal lattice Unit cell smallest part of a lattice that can be used to create full lattice Crystalline Solids 2D unit cell example The unit cell is a square Each corner contributes of a circle to the unit cell Net of 1 circle unit cell one circle but not necessarily in one piece The entire lattice can be formed by adding unit cells to each face Cubic Unit Cells Crystals have 3D unit cells There are 7 types The simplest are the cubic cells Faces meet at 90 with equal length sides cube Cubic cells are divided into 3 sub types simple or primitive cubic sc body centered cubic face centered cubic Cubic Unit Cells Primitive simple cubic Atoms sit at the corners of squares Layers stack atom on atom One atom cell 8 x 1 8 Atoms occupy 52 of the total volume 1 6 at rear 4 5 3 2 Cubic Unit Cells Body centered cubic An extra unshared atom sits in the center 8 x 1 8 1 2 atoms cell An atom in the diamond gap 68 of the space is occupied Cubic Unit Cells Face centered cubic 1 atom at the center of each face Face atoms are shared by 2 cells 6 x 8 x 1 8 4 atoms cell 74 of the space is filled by atomsupper limit Closest Packing of Spheres Metal crystals have equal sized atoms spheres In closest packing each atom has 6 neighbors layer Single layer Largest amount in the closet layer Closest Packing of Spheres Layers stack with the atoms in one layer resting in holes of another hexagonal close packing An abab structure This is also the fcc structure but seen from a different perspective Look exactly same layer and position b a b a Closest Packing of Spheres Start with ab b layer in a holes Add another a layer Green directly over green Closest Packing of Spheres Cubic Close Packing has an abcabc structure the unit cell is face centered cubic a c b a Cubic Close Packed Start with ab b layer in a holes Add c gold above holes in the original green a layer Which packing scheme gives the highest density of spheres A Simple cubic B Hexagonal close packing C Body centered cubic Ionic Crystal Structures Ionic crystal structures are more complex The ions making up the crystal are not identical to each other may be of very different sizes may have different number of charges may not be spheres polyatomic ions Ionic Crystal Structures Many ionic compounds have sc or fcc negative ion lattices anions are usually larger Csl Simple cubic l Unit cell 8 x 1 8 1 l and 1 Cs Ionic Crystal Structures NaCl has an fcc Cl lattice Na in octahedral holes Each Na is surrounded by 6 Cl Each Cl is surrounded by 6 Na Ionic Crystal Structures The NaCl unit cell contains 4 Cl ions 8 corners x 1 8 Cl corner 1 Cl 6 faces x Cl face 3 Cl It also contains 4 Na 12 edges x Na edge 3 Na 1 center x 1 Na center 1 Na


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