CHEM 122 1st Edition Lecture 7Outline of Last LectureI. Clausius-Clapeyron Equationa. Relate to a straight lineII. Phase Diagramsa. Phase Diagram Components Outline of Current Lecture I. Solidsa. Crystallineb. AmorphousII. Structure of a CrystalIII. Cubic Unit Cellsa. Simple cubicb. Body-centered cubicc. Face-centered cubicIV. Packing Identical SpheresV. Number of particles per unit cellVI. Closest Packing of Identical SpheresCurrent LectureSolids:These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best Used as a supplement to your own notes, not as a substitute.- Crystalline Solid: Has particles (atoms, ions, molecules) arranged in a well-ordered structure.o Distinct 3-D structure with a well defined melting point- Amorphous Solid: Does not have a well-ordered structure.o Doesn’t have a distinct 3-D structure and slowly softens over a broad temperature range.- Crystal Lattice: overall pattern- Unit Cell: Smallest pattern that repeats in all directions.o Crystalline solid is composed of nearly infinite number of identical unit cells.o Generally 6 sidedo 7 types of unit cells; only need to be able to identify Simple Cubic and Hexagonal. Simple Cubic: Basic cube with all sides the same and all angles at 90 degrees. Hexagonal:2 sides equal but the 3rd one doesn’t. 2 angles equal 90degrees and the other one equals 120.- What controls a Crystal Structure? o Relative size of the particleCubic Unit Cell: Three Kinds:- Simple Cubic: a cube with particles only at the 8 cornerso Each particle in the corners is shared by 8 unit cells so that means each particle is split into 8. Having 8 cells with, 1/8 of a particle in each unit cellthere is one particle total in each unit cell. (1/8)8=1- Body-Centered Cubic (bcc): A cube with particles at the 8 corners plus one more in the center of the cube.o Each particle in the corner is shared by 8 unit cells, meaning that each particle is split into 8.The particle in the middle is not split, leaving 2 particles per unit cell. 8(1/8)+1(1)=2- Face-Centered Cubic (fcc): a cube with particles at the 8 corners plus 6 more in the center of each face of the cube.o Each particle in the corners is shared by 8 unit cells, meaning that each particle is split into 8. The face-centered particles are shared by only 2 unit cells, so the total particles per unit cell is 4. 8(1/8) + 6(1/2)=4- Many metals either have face-centered or body-centered cubic structures.- Coordination Number: how many of each particle is touching other particles.4 Ways to Pack Identical Spheres:- Simple Cubic:o Arrangement of identical Spheres in a simple cube.o Coordination number of 6 giving it a octahedral hole- Body Centered Cubico Arrangement of spheres in a Body-centered cube.o Coordination number of 8.- Closest-packed o Packing of spheres: a structure made up of one sphere surrounded by 6 others to maximize particle contact in 2-D- Hexagonal Closest packed- Cubic
View Full Document
Unlocking...