Materials Science Exam 1 Study Guide - Materials Science Exam 1 Study Guide Chapter 1 Metals Strong ductile thermal and electrical conductivity opaque

Materials Science Exam 1 Study Guide - Materials Science...

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Materials Science Exam 1 Study Guide Chapter 1 Metals: Strong, ductile, thermal and electrical conductivity, opaque, reflective Polymers: Covalent bonds, soft, ductile, low strength, low density, thermal and electrical insulators, transparent Ceramics: Ionic bonds of metallic and nonmetallic elements, brittle, glassy, elastic, insulators Chapter 2 Atomic number- number of protons in the nucleus = number of electrons Atomic weight- weight of 6.022*10^23 molecules, average weight considering all isotopes Valence electrons- electrons in unfilled shells, outer shells, participate in interatomic bonding Electron Configurations- use the atomic number order is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 4d s = 2 marks p = 6 marks d = 10 marks Periodic table and valence structure- columns have similar valence structure
Periodic table and electronegativity: Ionic bond- transfer of electron, metal donates and nonmetal accepts, requires large difference in electronegativity. Covalent bond- share electrons, similar electronegativity required Metallic bond-when a metal donates all of its valence electrons to a sea of free electrons Van der Waals- weak, caused by attraction between two dipoles Formulas to know: % ionic character, coeff of thermal expansion Chapter 3 Atomic packing factor (APF)- volume of atoms in unit cell/volume of unit cell Coordination number- number of nearest neighbor atoms Body centered cubic structure (BCC)- 2 atoms/unit cell = 1 center + 8 corners (1/8) Coordination # = 8, APF = 2 4 3 π ( 3 a 4 ) 3 a 3 = 0.68, a = 4 r 3 Large electronegativity (gain e-) Small electronegativity (lose e-) - 1 e- -2 e- -3 e- +1 e- +2 e-
Face centered cubic structure (FCC)- 4 atoms/unit cell = 6 face(1/2)+8 corners(1/8) Coordination # = 12, APF = 4 4 3 π ( 2 a 4 ) 3 a 3 = 0.74 , a = 4 r 2

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