CHM135H1 Lecture Notes - Lecture 10: Coordination Number, Covalent Bond

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CHM135H1 Full Course Notes

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The material has to be continually repeating themselves, and we have to be able to describe it as a unit cell now we have to understand the contents of the unit cell. If you drop a cube at the top, the bottom lattice points are on top of the other boxes, 1/8th of an atom is projecting into the unit cell we"re looking at. Total of 1 atom sitting in the box sitting in there in parts. Coordination number: # of nearest atoms that they have around it. Efficiency where we pack atoms into a cube = 52% (volume they occupy: lattice points found on each corner. Differs from simple because there is one more lattice point in the centre of the cell. The atom in the middle have 4 neighbours at the top, and 4 below it. This implies every atom should have 8 surrounding neighbours.

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I need help answering pages 104-106

103 UNIT CELL GEOMETRY INTRODUCTION These cells are Most solids form crystal lattices composed of repeating box-like units (unit cells). These ce parallelepipeds whose shape is determined by the lengths of the edges of the parallelepipeds an between the edges. A cubic cell has 90Â° angles between all of its neighboring edges and all of its edge are equal to each other There are three possible arrangements of atoms within a cubic cell. In a simple cubic unit, there is an located at each corner of the cube (and each corner atom is shared by seven other ce atoms present in a simple cubic unit cell. Corner atoms touch each other (exce atom ere are no other pt in the diagonal direction) In a body-centered cubic unit, there are corner atoms (as in the simple cube), but, in addition atom completely within the body of the cube that is not shared with any other cell. In the body-centered eu cell, none of the corner atoms touch each other but they all touch the central atom bic In a face-centered cubic unit, there a there is an atom centered on each of the six faces of the cell. Half of a face-centered atom belongs to re, again, corner atoms shared with the surrounding cells. In addition, toms, The other half belongs to the cell adjacent to that face. Each face-centered atom touches its four corner a but the corner atoms do not touch each other PROCEDURE The class should divide into eight groups and each group will check out a cubic cell model kit. Each kit 1. should contain: 8-1/8 spheres; 6-1/2 spheres; 1 - whole sphere; metal connecting rods Consult the diagrams in your textbook and build a simple cubic unit cell. Collaborate with the seven other 2. 3. 4. 5. groups of students and assemble a model of a portion of a solid formed from eight simple cubic unit cells Draw a diagram of a simple cubic unit cell and answer the questions on the report sheet for this cell type Repeat steps 2 and 3 for the body-centered and face-centered cubic units Observe your profess or's demonstration of a hexagonal unit cell and answer the questions on the report sheet.

1- Calculate the volume of one unit cell in fcc silver. Giveanswer in units of nm3 and in cm3.???

2-How many unit cells are contained in a 30 cm3 block of fccsilver????

3-Sketch the (2?1) plane and its intercepts????

4-All unit cells, no matter the shape, have the samelattice-point positions for the eight cell corners. Sketch a

unit cell and label the cell corner positions????

5-Starting from the origin, list the first three lattice points(including the 000 point) lying on the [121]

direction in the fcc lattice. Illustrate your answer with asketch showing enough unit cells to show where the

three points are.?????????

6-. a) Sketch the unit cell of a bcc metal (which has an atomplaced at each lattice point) and shade in the

(010) plane. Draw just one unit cell. This plane intersects thecenters of how many atoms in one unit cell????

7- Repeat part (a) except use the (020) plane. Again, just oneunit cell.?????

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CHM135H1 Lecture Notes - Lecture 10: Coordination Number, Covalent Bond

CHM135H1 Full Course Notes

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