ENGR 220 Lecture 2 Chapter 2
Week 2 Homework Problems Chapter 3 3.3, 3.6, 3.7, 3.14
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Structures in Solids A. Atomic Scale 1. Electronic structure of atoms 2. Bonding within atoms B. Angstrom (A, 10^-10m) to Nanometer (nm, 10^-9) Scale 1. Atomic.ionic arrangements in solids 2. Crystalline Solids C. Nano to Micron+ Scale 1. Grains D. Atom 1. Electron 2. Protons 3. Neutrons E. Atomic Number 1. # of Protons in nucleus of atom 2.# of Electrons in neutral species F. Atomic mass unit = amu = 1/12 mass of 12C G. Atomic wt. = wt. Of 6.023 x 10^23 molecules or atoms 1. 6.023 x 10^23 atoms of C weigh 12.011gm
I1.
Electronic Structure of Atoms A. Quantum mechanics 1. Governs atomic/subatomic particle behavior B. Bohr atomic model 1. Early attempt to describe the e- position and energy 2. Assumed e- revolved around nucleus in discrete orbitals 3. Only certain energy levels allowed a) Absorption of energy jump to higher level b) Emission of energy jump to a lower level 4. Limitation: unable to explain various e_ phenomena observed C. Wave Mechanical Model 1. E_ no longer considered as particles in discrete orbitals 2. E_position defined by probability of an e_
III.
Outcomes of Quantum Theory
A. Confining a particle results in quantization of the energy B. No two particles can have the same quantum numbers
IV.
Aspects of Materials A. Processing B. Structure C. Properties D. Performance
V.
Electronic Structure A. Exhibit both wave-like and particle-like behavior 1. Electrons located in orbitals defined by a probability 2. Each orbital at a discrete energy level defined by quantum numbers B. Quantum #.... Designation N (principal)... . K,L,M,N,O (1,2,3...) L = Subsitary.... ...s,p,d,f
VI.
To avoid confusion A. Lower Energy 1. Thing of a well, the deeper the well the lower the energy 2. More stable everything wants to be in the lowest state of energy
VII.
Electron Configuration A. For most elements the electron configuration is not stable B. Valence Electrons 1. Unfilled shells 2. Filled shells are more stable 3. Valence electrons are most readily available for bonding and tend to control the chemical, electrical, thermal and optical properties 4. Determine Electronegativity A. Electron Greed Left to Right Bottom(lower) to Top (higher
VIII.
IX.
Types of Bonds A. Primary Bonds Usually strong 1. lonic 2. Covalent 3. Metallic B. Secondary Bonds usually much weaker 1. Van der Waals
X.
Ionic Bond A. Simplest and an analytical expression exists making comparisons w. Experiment
possible
B. Metal (Donates Electrons) + Non Metal (accepts electrons) C. Cations an