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80 Cards in this Set
- Front
- Back
how do metals pack?; |
•solid spheres • radius is identical for atoms of the same element •packing tight together as tight as possible |
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how the second layer is packed; |
• forms upon the lattice • the second layer of atoms fits into the gaps on the first layer |
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•if they are on top of each other layer; [4] how they are related to one another |
•simple cubic •vertical pattern, of AAAA •coordination no of 6, as each atom has 6 nearest neighbours •related by octahedrsl symmetry |
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how the third layer sits; [4] give an example too |
•sits on top of the first layer •repeat unit of ABABAB •where each atom has 8 nearest neighbours, with a coodination no of 8 • e.g. Fe |
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how alternative packing occurs; |
•most efficent for each atom, to have 6 nearest neighbours in one plane |
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how does the next layer form; |
•with the atoms sitting in the depressions |
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what are ccp and hcp? what are they both based on? |
•2 simple regular lattices, that achieve the highest density. •both have a coordination no of 12 •both based on their symmetry |
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name whether it is hcp or ccp |
•hcp |
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name whether it is hcp or ccp |
ccp |
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examples of HCP; |
•Mg, Zn, Be |
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examples of CCP; |
•Ca, Ni, Pt, Cu, Au, Al |
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•hcp |
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•ccp |
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what packing has a higher effiency? ; |
• hexagonal packing as it is 100% efficient •ccp leaves 26% vacant • but ccp still the most efficient packing of spheres. |
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define 'vacant' packing; |
•allows smaller molecules to penetrate the lattic |
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define interstitial sites; |
•in ionic systems •where the larger ions adopt one of the lattices, and smaller ions fit inbetween •sites can either be tetrahedral or octaherdral |
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if there are as many octahedral interstitial sites as ions in the lattice then... |
there are twice as many tetrahedral sites as ions in the lattice. |
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label 1 and 2 |
1 2r 2 r+h |
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what structure does NaCl form; [2] |
•chloride ions form cubic packed lattice and sodium ions in full octahedral interstitial sites •overall charge neutrality must be obeyed. |
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fill in the table for ccp |
1 all 2 1/2 3 1/3 4 all 5 1/2 |
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for ccp, label 1-5 |
1 NaCl 2 CdCl2 3 CrCl3 4 Na2O 5 ZnS |
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for hcp |
1 all 2 1/2 3 1/3 4 1/2, zinc blende |
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for hcp |
1 FeS 2 CdI2 3 FeCl3 4 ZnS, wurtzite |
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Unit cells; bricks form wall, like unit cells form crystal lattices |
•simplest repeat unit of a structure, that imparts all the necessary info to expand structure in all directions to generate the crystal called unit cell • |
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where it can be |
or |
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unless the ion is at the centre of a unit cell it will be shared... |
•between adjoining cells |
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•where an ion in the centre of a face is shared by... one on the edge... one on the corner... |
•2 cells in the centre • one on edge by four cells • one on the corner by 8 cells |
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in order to get a chemical formula, what should be known... |
•positions within a cell should be known |
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pic of the relation ship between the |
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what dictates how ions pack in a crystal [2] ; |
•size of cations and anions • ions pack to minimise replusion |
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E.g. if there are a bunch opf large positive charges what is needed ... and why... [2] |
•alot of smaller negative charges to pack around it •so replusion is minimised |
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how can the arrangement of atoms be determined in a crystal; |
•xray diffraction, as the ions pack in a crystal |
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how are crystal cells formed? |
• by 3D array of points (atoms) |
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define a unit cell; |
•smallest piece of the crystal required to show a repeating a pattern. |
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define a crystal lattice; |
•is the long range pattern that is shownh by repeating the unit cell |
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Hexagonal close packing; [4] |
•starts with a layer of identical spheres •2nd layer sits in the gaps of the first layer •3rd layer falls directly on too of first layer •ABABAB layer |
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Cubic close packing; also known as face centred cubic; [4] |
• start with a layer of identical spheres • 2nd layer, spheres in the dips forming AB layer. •3rd layer, places spheres into remaining gaps of the first layers •forms ABC layer, particles per unit cell. |
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Body centered cubic (bcc); [3] |
•particle in centre of a celland one at each corner • as there are 2 particles per unit cell •unit cell= one in the middle • 8x(1/8ths) at corners |
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example of a unit cell; |
• perovskite is a unite cell •contains titanium at the centre •6 oxygen, centre of faces • 8 Ca, at the corners |
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how the formula is decided; |
•by multiplying no. of ions by their occupancy |
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what perovskite unti cell contains and the calculations; |
• 1Tix1= Ti •6Ox1/2= 3O •8Ca x 1/8=Ca so the formula is CaTiO3 |
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what would the alternative unit cell contain?; |
• Ca at the centre, O ions are half way down each of the 12 edges •titanium ions occupy each of 8 corners so formula is the same |
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where Bravais lattices; |
•14 distinct families of unit cell |
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where the basic catergories have unit cell edge lengths (a, b, c) and internal angles (gamma, alpha, beta), α, β, and γ |
where the basic catergories have unit cell edge lengths (a, b, c) and internal angles (gamma, alpha, beta), α, β, and γ |
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label 1-7 |
1 cubic 2 tetragonal 3 orthorhombic 4 monoclinic 5 triclinic 6 trigonal 7 hexagonal |
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name the systems |
1 cubic 2 tetragonal 3 monoclinic 4 orthorhombic 5 rhombohedral 6 hexagonal 7 triclinic |
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within each lattice can there be more than one type; if so give an example |
•yes
•reflection, inversion, rotation |
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what are the 3 broad categories for solid state materials; |
• conductuing • insulating • semiconducting |
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define conducting; |
• electrons free to move throughout solid |
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define insulating; |
•electrons localised |
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define semi-conducting; |
•conductivity variable, and temp related |
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in the case of metallic conductivity, for every atomic orbital involved in the bond... |
• a molecular orbital is formed |
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the greater the number of bonding metal atoms the more... give an example |
•atomic orbitals combine for form molecular orbitals. Li ground state is 1s2 2si |
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label which Li types |
1 li 2 li2 3 li3 4 lin |
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how electrons are filled in a conductor; |
•partly filled band so electrons can move
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how electrons are filled in a insulator; |
•filled band and empty with a band gap too high in energy for electrons to cross |
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how electrons are filled in a semi-conductor; [3] |
•electrons can cross the small band • ntype semiconductors contain electrons in the 'empty' band •p type semicondutors have 'vacancies' in full band |
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how can semiconductors be formed? what it is doped with and alternative doping agent |
•addition of elements to tetravalent silicon, that have more or less than 4 valence electrons. • by doping it wih As (5 valence electrons), giving the n type semiconductor, electron rich. •doping with boron, 3 valent electrons gives p type semi conductor, electron deficient. |
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•n type semiconductor |
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what are the type of defect structures; [3] |
• schottky •frenkel • twinning |
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name |
twinning |
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name |
frenkel defect |
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name |
schottky |
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name |
simple cube |
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name |
body centered cubic |
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name |
face centered |
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name |
simple tetragonal |
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name |
body centered tetragonal |
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name |
orthorhombic |
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name |
rhombohedral |
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name |
simple monoclinic |
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simple hexagonal |
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triclinic |
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name |
cubic |
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name |
tetragonal |
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name |
monoclinic |
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name |
orthorhombic |
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name |
rhombohedral |
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hexagonal |
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triclinic |