DOC PREVIEW
BU CHEM 108 - Solids, Structures and Applications
Type Lecture Note
Pages 3

This preview shows page 1 out of 3 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 3 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 3 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

Lecture 5 Current LectureChapter 12: Solids: Structures and ApplicationsThe Solids State:- Crystalline Solid: Substance exhibiting an ordered array of atoms, ions, or molecules.o Metallic elements generally form these kind of solids- Amorphous Solid: Substance with a random ordering of atoms.Stacking Patterns:- Crystal Lattice: Ordered three-dimensional array of particles in a crystalline solid. - Hexagonal Closest-Packed (hcp): A crystal structure in which the layers of atoms or ions have an a-b-a-b-a-b stacking pattern. - Cubic Closest-Packed (ccp): A crystal structure in which the layers of atoms, ions, have an a-b-c-a-b-c-a-b-c stacking pattern- Square Packed: A structure where the atoms are arranged in an a-a-a stacking pattern- Two square-packed: a structure where the atoms are arranged in an a-b pattern, This pattern is just like the square packed but with two different layers of atoms.Unit Cells:Basic repeating unit of the arrangement of particles in a crystalline solid.- Coordination number : The number of other particles each particle is in contact with o For ions, it is the number of oppositely charged ions an ion is in contact with - Higher coordination number means more interaction, therefore stronger attractive forces holding the crystal together - The packing efficiency is the percentage of volume in the unit cell occupied by particles o The higher the coordination number, the more efficiently the particles are packing togetherVolume of the unit cell and packing Efficiency: - Packing Efficiency: Percentage of the total volume of the unit cell occupied bythe atoms.o Equation: ((Volume Occupied by spheres)/ (Volume of Unit cell))*100%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. Chem 108 1st EditionLecture 5 - Vsphere = 4/3 π r3 For simple cubic, with one atom per unit cell, this represents the volume of space occupied by the atom.o Example:With l = 2r: Volume of the unit cell is: V unit cell = l3 = (2 r)3 = 8 r3Packing efficiency = V sphere/ V unit cell = 4/3 π r3 /(8 r3 ) = π/6 = 52%Types of Unit Cells and their dimensions:- Hexagonal Unit Cell (hcp): unit cell for hexagonal closest packing.o Coordination number: 12o Packing Efficiency: 74%- Simple Cubic (sc): square-packing arrangement; particles located at 8 corners of cubic unit cell. Eight particles, one at each corner of a cubeo Atoms touch along cell edge. (radius of atom) × 2 = l (length of the unitcell)o # of total atoms in the cell: (1/8)*8=1 whole atomo Relationship between r and l: r = l/2 = 0.5lo Coordination number: 6o Packing Efficiency: 52%- Body-Centered Cubic (bcc): square packing arrangement in which particles are located at 8 corners and one in the center of cubic unit cell.o Atoms touch along body diagonal. (radius of atom) × 4 = l × √3o # of total atoms in the cell: ((1/8)*8) +1 =2 whole atomso Relationship between r and l: r = (l√3)/4 = 0.433lo Coordination number: 8 o Packing Efficiency: 68%- Face centered cubic (fcc):Closest packing unit cell in which atoms are located on the 8 corners and 6 faces of a cubeo Atoms touch along face diagonal. (radius of atom) × 4 = l × √2o # of total atoms in the cell: ((1/8)*8) + ((1/2)*6) =4 whole atomso Relationship between r and l: r = (l√2)/4 = 0.3536lo Coordination number: 12 o Packing Efficiency: 74%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. Chem 108 1st EditionLecture 5 -Density of unit cells: - D=m/v o m is the weight of the atoms in the unit cell Ex: unit cell mass = (# of atoms) x (atomic mass of atom/ion in g/mole) / (6.022 x 1023 atoms/mole)v is the volume of the cube Ex: l3 just find l in terms of r if need be.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. Chem 108 1st


View Full Document

BU CHEM 108 - Solids, Structures and Applications

Type: Lecture Note
Pages: 3
Documents in this Course
Load more
Download Solids, Structures and Applications
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Solids, Structures and Applications and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Solids, Structures and Applications 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?