222 Exam 1 - TRUE/FALSE Radicals dont change their identity...

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TRUE/FALSE Radicals don’t change their identity during chemicals reactions. Melting T of polymers is typically increasing with their molecular weight Atomic number is equal to the number of protons in nucleus atom Valence electrons determine most of properties The atoms in the same row (period) on the periodic table have the same quantum number The atoms n the same column (group) on the periodic table have the same number of valence electrons Thermal expansion coefficient is inversely proportional to atomic bonding energy Non crystalline solids are called as an amorphous material The close – packed direction of FCC is <110>, of BCC <111>, HCP <1120>, simple cubic <100> The close packed planes of FCC is {111}, BCC {110}, HCP {0001}, simple cubic {100} “n” is the principal quantum number and it is related to the radius of subshells BCC (68%) has a lower atomic packing density factor than FCC (74%) crystal structure A mer is the basic repeating unit in the polymer structure A slip plane contains the dislocation line and its burger’s vector The burger’s vector is parallel to the dislocation line for screw dislocation and perpendicular for edge dislocation Materials with higher melting point typically have a higher Young’s modulus Dislocation is one type of linear defects Crystals with hexagonal close packed (HCP) structure has 6 atoms in one unit cell Point defects appear in pair in ceramics because they need to achieve neutrally Fick’s 2 nd second law describes non steady- state diffusion Ionic bond is non directional while metallic bonding is non-directional Thermoplastic has linear or branched polymer structures Most polymers have amorphous structure and most metals have crystalline structure Interstitial diffusion is much faster than that of vacancy diffusion Second phase particle is a 3D defect Material science focuses on investigating the relationship between the structures and the properties of materials. Two electrons in an atom can have the same four quantum number. (F) A material of which melting temperature is high has typically low elastic modulus. (F)
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TERMS & CONCEPTS 6 Classifications of the properties of the materials: mechanical, electrical, thermal, optical, magnetic, biocompatible, and corrosion resistance. Bohr Atomic Model: describes the position and energy of the electrons. It arranges electrons according to energy levels. Wave Mechanical Model : electrons are treated as particles + waves. Describes electrons with 4 quantum numbers (l, n, ml, ms) Electronegativity : is the tendency of an atom to share or gain electrons. The ability of an atom  in a molecule to attract electrons to itself. EN higher from L to R and from B to T (atomic radius gets smaller because R has more protons and shrink energy) Pauli Exclusion Principle: electrons in the same atom or electrons from different atoms which
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This note was uploaded on 09/24/2011 for the course MEEN 222 taught by Professor Radovic during the Spring '08 term at Texas A&M.

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222 Exam 1 - TRUE/FALSE Radicals dont change their identity...

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