AtomicStructureAndBonding

AtomicStructureAndBonding - TOPIC 2: ATOMIC STRUCTURE &...

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Unformatted text preview: TOPIC 2: ATOMIC STRUCTURE & BONDING Properties Structure Processing • Electronic level (subatomic) • Atomic (molecular level, chemical composition) • Crystal (arrangement of atoms or ions wrt one another) • Microstructure (can study with microscopes) • Macrostructure (can see with naked eye) “Materials Science” “Materials Engineering” OUTLINE • What promotes bonding? • What types of bonds are there? • Bonding material properties (melting point, thermal expansion, elasticity) TOPIC 2: ATOMIC STRUCTURE & BONDING • Electronic structure & bonding (Review: freshman chemistry) Based on Chapter 2 (Callister) Nucleus: Z = # protons = 1 for hydrogen to 94 for plutonium N = # neutrons Atomic mass A ≈ Z + N Adapted from Fig. 2.1, Callister 6e. BOHR ATOM electrons: n = principal quantum number n=3 2 1 n labels shells; shells are composed of sub-shells: s, p, d, f, … • have discrete energy states • tend to occupy lowest available energy state. Electrons... ELECTRON ENERGY STATES Maximum electrons In sub-shells s = 2 p = 6 d = 10 f = 14 Maximum electrons in n th shell = 2n 2 • have complete s and p sub-shells 8 electrons (octet) • tend to be unreactive . Stable electron configurations... Z Element Configuration 2 He 1s 2 10 Ne 1s 2 2s 2 2p 6 18 Ar 1s 2 2s 2 2p 6 3s 2 3p 6 36 Kr 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 Adapted from Table 2.2, Callister 6e. STABLE ELECTRON CONFIGURATIONS • Valence (outer) shell usually is not an octet. • Most elements: Electron configuration not stable . Why? Element Hydrogen Helium Lithium Beryllium Boron Carbon ... Neon Sodium Magnesium Aluminum ... Argon ......
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This homework help was uploaded on 02/26/2008 for the course MAT 33 taught by Professor Keith during the Fall '07 term at Lehigh University .

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AtomicStructureAndBonding - TOPIC 2: ATOMIC STRUCTURE &...

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