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Transcript

디자인과 재료 문제풀이 김석범 MSM Lab . ( Graduate Student ) 2014. 9. 23 Problem 2.1 Cite the difference between atomic mass and atomic weight Atomic mass ? Atomic weight ? Atomic weight = Average of each atomic mass 2 Problem 2.4 (1) Cite two important quantum-mechanical concepts associated with the Bohr model of the atom. - electrons are particles moving in discrete orbitals - electron energy is quantized into shells 3 Problem 2.4 (2) Cite two important additional refinements that resulted from the wave-mechanical atomic - electron position is described in terms of a probability distribution - electron energy is quantized into both shells and subshells - each electron is characterized by four quantum numbers (s,p,d,f) 4 Problem 2.4 sub (3) Why we use “Orbital” method? - Position - Momentum Uncertainty Principle Heisenberg 5 Problem 2.13 Calculate the force of attraction between a K+ and an O2- ion the centers of which are separated by a distance of 1.5nm = 2.05*10-10N 6 Problem 2.13 Preview 7 Problem 2.13 Preview 8 Problem 2.13 Preview 9 Problem 2.19 Compute the percent ionic character of the inter-atomic bonds for CsCl For TiO2? AX2 Crystal Structures 10 Problem 3 sub Why BCC , FCC , HCP are important? 11 Problem 3 sub Why BCC , FCC , HCP are important? 12 Problem 3.3 Show for the BCC crystal structure that the unit cell edge length a and the atomic radius R are related through 13 Problem 3.9 Calculate the radius of an iridium atom, given that Ir has an FCC crystal structure, a density of 22.4 g/cm3, and an atomic weight of 50.9g/mol 14 Problem 3.28 Compute the atomic packing factor for cesium chloride using the ionic radii in Table 3.4 and assuming that the ions touch along the cube diagonals. rCs + rCl- = 0.170 = 0.939 0.181 Since 0.732 < 0.939 < 1.0, cubic sites preferred So each Cs+ has 8 neighbor Cl- 15 Problem 3.28 Compute the atomic packing factor for cesium chloride using the ionic radii in Table 3.4 and assuming that the ions touch along the cube diagonals. 16 Problem 3.34 A hypothetical AX type of ceramic material is known to have a density of 2.65g/cm3 and a unit cell of cubic symmetry with a cell edge length of 0.43nm. The atomic weights of the A and X elements are 86.6 and 40.3g/mol, respectively. On the basis of this information, which of the following crystal structures is(are) possible for this material: rock salt, cesium chloride, or zinc blende? CsCl and ZnS 17