Close Packed Structures
Chapter Name : The Solid State |
Sub Topic Code : 102_12_01_07_02 |
Topic Name : Close Packed Structures |
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Sub Topic Name : Formula Of A Compound And Number Of Voids Filled |
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Introduction
• The number of the two types of voids in closed packed structures depends upon the number of close packed spheres. • Let the number of close packed spheres be N, then: The number of octahedral voids = N The number of tetrahedral voids = 2N • In ionic solids, the bigger ions (usually anions) form the close packed structure and the smaller ions (usually cations) occupy the voids.
Pre-Requisites:
Particles, solids, 2D and 3D close packing structure, octahedral and tetrahedral voids.
Activity:
Sal t and sugar crystals are arranged in 3 dimensional closed packed structures.
Real Life Question:
How are particles of solid arranged?
Key Words / FlashCards
| Key Words | Definitions (pref. in our own words) |
|---|---|
| coordination number | The number of nearest neighbors of a particle is called its coordination number. |
Learning aids / Gadgets
| Gadgets | How it can be used |
|---|---|
| Blocks, marbles | Use marbles or blocks to construct different types of closed pack structures. |
Real life uses :
Close packed structures are seen in variety of different substances, e.g. Salt, sugar.
Places to visit :
Kitchen
Practical examples around us
| Examples | Explainations |
|---|---|
| Salt, sugar crystal | A sugar crystal is compact and 3 dimensional cuboid structure. |
What you learn in Theory:
In ionic solids, the bigger ions (usually anions) form the close packed structure and the smaller ions (usually cations) occupy the voids. In a given compound, the fraction of octahedral or tetrahedral voids that are occupied depends upon the chemical formula of the compound.
What you learn in Practice:
The chemical formula of a compound gives a general idea of the packing of particles in solids.