ABCT4772-Structure and Properties of Solids-handout5.pdf -...

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Lesson Learning OutcomesStudents should be able to:1.Explain the followingterms: close-packed; polytype,coordinate number, (n+, n-) coordinate, metallic conductor,semiconductor, band gap, Fermi level.2.Describe the major types and their main features of thestructures adopted bymetallic solids3.Describe the bonding character ofionic solidsand thethree main types of structures classified based on theradius-ratio rule.4.Explain and present examples for thecovalent networksolids andmolecular solids5.Describe the termcrystal defectand the main types ofcrystal defects, their influence on the properties of crystal...Structureand Propertiesof Crystal
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Lesson Learning OutcomesStudents should be able to:6.Explain briefly and give examples of the differentmechanical propertiesdisplayed by the four types ofsolids.7.Describe the “tight-binding approximation” and based onthis model to explain the different features ofelectricalconductivityshowed by metallic conductor and semi-conductor.Structureand Propertiesof Crystal
Structureand Propertiesof CrystalInternal, microscopicBulk, macroscopicarrangements and identitiesof constituent atoms, ions,molecules, etc•Mechanical properties•Electrical properties•Crystal growth•Texture•Diffusion properties•CorrosionMetallic solidsIonic solidsCovalent network solidsMolecular solids andOthers•Others•Optical propertiesCrystal defectPhysicalChemical
Elemental metals are the simplest cases of thebonding within a solid (tight-bindingapproximation).Electronsin the metals aredelocalizedover arrays of identical cations andbind them together into arigidbutductile andmalleablewhole.Metallic solids
Most metallic elements crystallized in structures that can berationalized in terms ofhard spherical metal cationspackingtogether intoorderly arrays.There are mainlythree formsof arrangements:• two areclose-packed;• one isless closely packed.Close-packed 2D: a layer of spheres with maximum utilization ofspaceThe first layer of close-packedspheres used to build a 3Dclose-packed structure.Close-packed 3D structure is obtained by stacking such layeron top of one another.Metallic solids
The packing can be done in different ways givingstructures thatare identical in 2D but differ in 3D, denoted aspolytypes.Two close-packed structures1stlayer2ndlayer3rdlayer3rdlayerThe 2ndlayer liesin the depressionof the 1stlayer.The 3rdlayer reproducesthe 1stlayer, givingABABAB... patternThe 3rdlayer is placed overthe gaps of the 1stlayer,givingABCABC... patternHexagonally close-packed(hcp)Cubic close-packed(ccp), giving face-centered unit cell,denoted alsocubic FABAABAABCABCAAB
The compactness of close-packed structures is indicated by theircoordination number.Coordinate number: the number of atoms immediatelysurrounding any selected atom.Coordinate number ofhcpandccppolytypes are both12.
Less closely packed structure

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Term
Summer
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NoProfessor
Tags
Atom, Electron, Ion, Crystal
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The document you are viewing contains questions related to this textbook.
General Chemistry
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Chapter 20 / Exercise 20.10
General Chemistry
Ebbing/Gammon
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