MSE Note Test1.pdf - Chapter 1 • Properties of solid...

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Chapter 1 Properties of solid materials may be grouped into six different categories: mechanical, electrical, thermal, magnetic, optical, and deteriorative. 1.4 Classification of Materials Solid materials have been grouped into three basic categories: oMetals: Atoms are arranged in a very orderly manner. Relatively dense in comparison to the ceramics and polymers. Relatively stiff and strong. Ductile (i.e., capable of large amounts of deformation without fracture), and are resistant to fracture. Have large numbers of nonlocalized electrons. oCeramics: Compounds between metallic and nonmetallic elements. Relatively stiff and strong. Extreme brittleness (lack of ductility) and are highly susceptible to fracture. Insulative to the and are more resistant to high temperatures and harsh environments. oPolymers: Organic compounds that are chemically based on carbon, hydrogen, and other nonmetallic elements. Very large molecular structures. They are not as stiff or strong. Extremely ductile and pliable. Tendency to soften and/or decompose at modest temperatures. Low electrical conductivities. oComposites: Composed of two (or more) individual materials that come from the categories previously discussed. Chapter 2 2.2Fundamental Concepts Atomic Number: number of protons in the nucleus. Atomic Mass: sum of the masses of protons and neutrons within the nucleus. Isotopes: atoms of elements with two or more different atomic masses. Atomic Weight: weighted average of the atomic masses of the atom’s naturally occurring isotopes. In one mole of a substance, there are 6.022 x 10^-23 (Avogadro’s number) atoms or molecules.2.3Electrons in Atoms Quantum Numbers: oThe four electron quantum numbers are: n: electron orbital size (average distance from the nucleus)
l: orbital shape. Range of values: l = 0 to l = (n 1) ml: number of electron orbitals can take on integer values between -l and +l ms: spin moment (must be oriented either up or down). Two values are possible: +1/2 (for spin up) and -1/2 (for spin down). Electron Configurations: oElectron states: values of energy that are permitted for electrons oPauli exclusion principle: each electron state can hold no more than two electrons that must have opposite spins. oElectron Configuration: way these states are occupied.
Atomic Models: oBohr Atomic Model: early attempt to describe electrons in atoms, in terms of both position (electron orbitals) and energy (quantized energy levels). Electrons are assumed to revolve around the atomic nucleus in discrete orbitals. The position of any electron is defined in terms of its orbital. Energies of electrons are quantized oWave-Mechanical Model: Electron is considered to exhibit both wavelike and particle-like characteristics.

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Term
Fall
Professor
Fong
Tags
Materials Science, Atom, Tensile strength, Polymers

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