The key difference between crystalline and noncrystalline solids is that crystalline solids have an evenly distributed three-dimensional arrangement of atoms, ions, or molecules whereas non-crystalline solids do not have a consistent arrangement of particles.
Crystalline Solids and Non-crystalline Solids are the two main categories of solids that show some difference between them in terms of the arrangement of the constituent particles and other properties. They have differences in their geometries and other physical properties as well.
CONTENTS
1. Overview and Key Difference
2. What are Crystalline Solids
3. What are Noncrystalline Solids
4. Side by Side Comparison – Crystalline vs Noncrystalline Solids in Tabular Form
5. Summary
What are Crystalline Solids?
In crystalline solids, constituent particles (atoms, molecules or ions) arrange in a three-dimensional periodic manner. They bind with each other via planes or faces. The smallest repeating unit in these solids is “unit cell”. All the unit cells in a particular solid are identical and repeating. For example; unit cells are like bricks in a wall.
Diamond and Graphite: Examples of Crystalline Solids
Crystalline solids can also be categorized as follows.
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| Type | Constituents | Inter molecular Forces | Properties |
| Ionic Solids (Table salt – NaCl) | Positive and negative ions | Electrostatic attractions | Very high melting points, Poor conductors, Brittle |
| Molecular Solids (Sucrose) | Atoms and molecules | London dispersion forces and Dipole-Dipole attractions, Hydrogen bonds | Low melting point, Flexible, Poor conductors |
| Covalent Network (graphite, diamond) | Atoms | Covalent bonds, Weak London forces | Very high melting and boiling points, Poor conductors |
| Metallic Solids | Metal atoms | Metallic bonds | High melting point, Soft-malleable, Very hard, Good conductors |
What are Noncrystalline Solids?
Non- crystalline solids are “amorphous solids”. Unlike crystalline solids, they do not have a definite geometrical shape. The atoms in solids pack closely together than in liquids and gases. However, in non-crystalline solids, particles have a little freedom to move since they are not arranged rigidly as in other solids. These solids form after sudden cooling of a liquid. The most common examples are plastic and glass.
What is the Difference Between Crystalline and Noncrystalline Solids?
In crystalline solids, constituent particles (atoms, molecules or ions) arrange in a three-dimensional periodic manner. Non-crystalline solids do not have a consistent arrangement of particles. So, non-crystalline solids are amorphous solids. With regard to the geometry of these solids, crystalline solids have a well-defined geometrical shape due to the regular arrangement of unit cells, unlike Non-crystalline solids that do not have well–defined geometrical shape. Furthermore, crystalline solids have a long range order while non-crystalline solids have a short range order.
Crystalline solids have a high fixed value for the heat of fusion and a definite melting point. However, non-crystalline solids do not have a fixed value for the heat of fusion and they melt over a range. Moreover, crystalline solids are true solids. They show all the properties of solids. On the contrary, Non-crystalline solids do not show all the properties of solids. Therefore, they are called “pseudo solids”. Energy in crystalline solids is lower than that of non-crystalline solids.
Summary – Crystalline vs Noncrystalline Solids
The two main categories of solids are crystalline Solids and Non-crystalline Solids. The difference between crystalline and noncrystalline solids is that crystalline solids have an evenly distributed three-dimensional arrangement of atoms, ions, or molecules whereas non-crystalline solids do not have a consistent arrangement of particles.