Crystalline and Amorphous Solid Materials
Crystalline solid like molecular, ionic, covalent, and metallic crystals define orderly arrangement properties of constituents atoms, ions, and molecules but amorphous solids materials meanings the indefinite types of structure. From the definition of crystalline and amorphous solids, carbon forms diamond crystals and amorphous solid materials like graphite.
The rigidity due to the absence of the translatory motion of the structural units of the solids. In solids, very strong forces of attraction amongst the molecules or ions.
The strong forces of attraction due to the absence of translatory motion. Therefore solids have only the vibrational motion about their mean position.
When the external energy supplied to solids the molecules gain translatory energy along with vibrational energy. Thus the solid-state convert into the liquid state.
Molecular crystalline Solid Material
The molecular crystalline solid material is less compressible and denser than the liquid. Therefore according to the arrangement of the atoms, ions or molecule, they are classified into two broad types
- Crystalline Solid Materials
- Amorphous Solid Materials
Definition of Crystalline solid
Solid which posses a definite structure, sharp melting point, and symmetrical arrangement of constituents are called crystalline solid.
Therefore, these properties result to form a high degree of internal order that extends in a definite pattern. They show long-range order in the crystal.
For example, sodium chloride, potassium chloride, sugar, and ice, quartzes are the crystalline solid material that has a sharp melting point and a definite order arrangement.
Properties of Crystalline Solids
- In the crystalline solid, the constituents may be atoms, ions, molecules.
- Crystalline solids have the properties of sharp melting points, flat faces, and sharp edges. It has a well-developed form and usually arranged symmetrically.
- Definite and the ordered arrangement of the constituents extends over a large distance.
- Crystalline solids belonging to the cubic class shows enantiotropic properties. But the magnitude of the enantiotropic properties depends on the direction of measurement.
Definition of Amorphous Solid
Amorphous materials define as a solid which does not possess definite structure, sharp melting point, and the constituents like atoms ions, molecules do not form an order arrangements.
Therefore, the constituents extend over a short-range, called short-range order. Glass, pitch, rubber, plastics, etc has the properties of amorphous solids.
Amorphous solid materials define many characteristics of crystalline such as shape rigidity and hardness but do not order arrangement and melt gradually over a range of temperatures. Hence amorphous solids are considered as supercooled liquids rather than solid.
Difference between Crystalline and Amorphous Solids
- Crystals meanings a definite structure and a sharp melting point. But amorphous that do not define a definite structure and sharp melting point.
- The constituents of crystalline material are ordered arrangement which extends over a long-range. But in an amorphous material define the constituents that do not have order arrangement.
Types of Crystalline Solids
On the basis of the nature of force operating between constituent particles meanings atoms, ions, molecules, solid crystals are classified into four categories.
Molecular Crystalline Solid Material
Van der Waals’s types of forces hold the constituents in the molecular crystalline material. But this type of force is weaker thus the molecular crystalline solid material has low melting points and soft.
Examples of these types of crystals are solid CO2, CCl4, Ar, and most of the organic compounds and hydrocarbon.
Non-Polar Crystalline Solids
But some of these types of crystals are non-directional. Solid H2, He, O2, Cl2, CO2, and methane are examples of these types of crystals. Thus the forces operating between constituent particles atoms or molecules is a weak London force of attraction.
Polar Binding crystal solids
This type of crystal shows the polar character. SO2 and NH3 are examples of this type of crystals. Thus dipole-dipole attraction forces operating between the constituents atom of these molecules.
Ionic Crystals solid
Ionic crystals meanings the nondirectional electrostatic forces of attraction operating between the oppositely charged ions, they are strong and likely to be brittle.
They pass electricity, high heat for melting and boiling point, and can not be bent.
But the melting point of the ionic crystals increases with the decreasing size of the constituent particles. Because some of the atoms may be held together by covalent bonds to form ions having a definite position and orientation in the crystal lattice. CaCO3 is an example of ionic crystals.
Covalent Crystalline Solid
The forces involved here chemical bonding or covalent bonds extended in three dimensions to form giant type molecule.
Therefore covalent crystalline solid material is strong and hard solids with high melting points. Diamond, silicon are examples of these types of crystal.
Definition of Metallic Crystals
Electron held loosely in these types of crystals structure. Therefore they are good conductors of electricity. Metallic crystalline solid can be bent and strong.
Since the forces have non-directional and the arrangement of atoms frequently corresponds to the closet packing of the sphere.
Crystalline and Amorphous Solid of Carbon
Carbon has several covalent crystalline and amorphous solid forms in nature. Diamond crystals and graphite material show different properties and structure although they form by the same atom like carbon.
Four other rare and poorly understood properties of carbon crystal are β-graphite, Lonsdaleite or hexagonal diamond, Chaoite (very rare mineral), and carbon VI.
But the last two forms of carbon appear to contain -C≡C-C≡C- and closer to the diamond in their properties.
Amorphous Solid Graphite
The various material like carbon black, soot, etc. are amorphous solid but all of these forms micro-crystalline structure.
Amorphous Graphite consists of a layer structure in each layer the C-atoms arranged in hexagonal planner arrangement with SP2 hybridized. It contains three sigma bonds to three neighbors and one π-bonds to one neighbor.
Hence the resonance between structures having an alternative mode of π bonding. It makes all C-C bonds equal with the bond order of 1.33.
Therefore the π electrons responsible for the electrical conductivity of amorphous graphite material. Successive layers of carbon-atoms attached by weak van der Waals forces with separation of layers 335pm. Thus the graphite layers easily slide over one another and define an amorphous solid material.
Diamond Crystals Properties
Each SP3 hybridized carbon meanings tetrahedrally surrounded by four other carbon atoms with a C-C bond distance of 154 pm in the diamond crystals. These tetrahedral structures form a cubic crystal unit of the diamond.
Thus carbon has properties to forms both crystalline and amorphous solid materials for our universe.