Classification of Solids Based on Crystal Structure

Introduction

The most common sort of solid material found in nature is crystalline solids. They are composed of atoms, ions, & molecules arranged in exact & repeating 3-D patterns, resulting in a crystal lattice that spans in all directions in a well microscopic structure. Unlike amorphous materials, crystalline solids have discrete melting temperatures. Network atomic, metallic, ionic, & molecular solids, as well as real solids, are all crystalline solids. Crystals have generally sharp, well-defined melting temperatures, owing to the uniformity of the crystalline lattice, which creates identical local conditions. As an outcome, the solid's intermolecular interactions are consistent, & each contact requires the same quantity of thermal energy to break at the same moment.

Difference Between Crystalline and Amorphous Solids

Crystalline solids	Amorphous solids
The constituent particles are arranged in a consistent pattern with both short- as well as long orders.	Individual substances are not arranged in any certain arrangement. There might be just a very short-term order.
Across every sense of the term, they are solids.	Supercooled liquids or even pseudo solids are amorphous solids.
Their melting temperature is exceedingly high.	At varying temperatures, amorphous substances melt.
They have a unique heat from fusion.	They have no detectable fusion heat.
Geometrically specified crystalline solids	They come in a range of shapes & sizes.
The cleavage of crystalline solids is smooth.	They're carved in an irregular design.
They are Anisotropic.	They're isotropic.
E.g., Quartz is composed of crystalline SiO2.	E.g., Amorphous SiO2 is used to make silica glass.

Forms of Solids

They are categorised into 3 forms depending on the nature of their chemical bonding,component particle configuration, as well as composition.

Crystalline Solids

They are a collection of tiny crystals, each with its distinct geometric shape. The component particles are arranged in a consistent pattern of long-range order. This pattern continues in the crystal regularly. A crystal lattice is a symmetrical 3-D arrangement of atoms within a crystal. The component particles of a crystal lattice are depicted as points. E.g., sugar as well as common salt.

Amorphous Solids

It has no form & is composed of irregularly shaped particles. As opposed to crystalline materials, the particle distribution is in short-range order. Although they feature consistent repeating patterns, they can only be seen across small distances. Therefore, the particle distribution is exceedingly disorderly. E.g., rubber, glass, as well as plastic.

Isotropy and Anisotropy

The term isotropic originated from the Greek terms isos (equal) plus tropos (way). Some substances, such as diamonds, metals, & glasses, have the same material characteristics in all orientations; these substances are considered isotropic materials, & their behaviour is known as isotropy.

The term anisotropic originated from the Greek terms a (without), isos (equal), plus tropos (way). As a result, anisotropic significance has various qualities in different directions. It is the inverse of isotropic. Anisotropic substances include wood as well as composite materials. These substances' qualities are directionally dependent, which means they exhibit distinct properties in various directions. It refers to the behaviour of certain materials.

Space Lattice and Unit Cell

A space lattice is a pattern of points that repeats itself in space. Because it is a repeating pattern, a tiny segment of the lattice that when repeated in various directions, generates the entire space lattice. The 'unit cell' is a tiny section of the lattice.

Therefore, space lattice refers to the regular distribution of the component constituents of a crystal - atoms, ions, or molecules in 3-D space.

A unit cell is the smallest 3-D portion of a full space lattice that keeps repeating in multiple directions to generate the entire space lattice.

Since the lattice may be built by piling unit cells, it can be regarded as the essential building block of the crystal lattice.

Crystal Systems

It is one of the many different types of crystals, space groups, & lattices. In crystallography, the lattice system, as well as the crystal system, are related with a little variation. Crystals & space groups are classified into 7 crystal systems depending on their point groups.

The 7 Crystal Systems approach to categorization is based on the lattice & atomic structure. The atomic lattice is made up of a succession of atoms that are arranged in a symmetrical arrangement. The lattice may be used to identify the appearance & physical qualities of the stone. It is possible to tell which crystal system they are from. Crystals are considered to symbolise the element earth in a Cubic System.

The seven crystal systems are

• Cubic

• Hexagonal

• Tetragonal

• Monoclinic

• Orthorhombic

• Triclinic

• Trigonal

Conclusion

Crystalline solids are not isotropic in existence. They are anisotropic, which means they have diverse properties in different directions. They have a sharp melting temperature, extended-range order, as well as specified regular geometry. Crystalline materials' atoms or even molecules have a certain regular shape. Crystal lattices that stretch in all directions are produced by crystalline substances in general. They are another name for true solids. The 4 types of crystalline solids are ionic, covalent, metallic, & molecular solids. E.g., diamond, sodium chloride, as well as sodium nitrate.

FAQS

1. Why is graphite, a covalent solid, such a superb electrical conductor?

It is a covalent solid because all its constituents are linked by covalent bonds. Covalent solids are frequently poor conductors of electricity as there are no free electrons (e^-) to travel within the crystal. Graphite is an exception because the carbon atoms are bonded in a hexagonal arrangement & exist in layers. Because of this hexagon layered structure, 1 e^- out of every 4 carbon atoms is free to travel out of each layer to carry electricity.

2. Is glass a crystalline substance?

It is a non-crystalline amorphous solid with a transparent look that is used in a wide range of utilitarian, technical, & decorative applications, including window panes, tableware, as well as optics. Glass is often formed by rapidly chilling a molten state, but, certain glasses, such as volcanic glass, occur spontaneously.

3. Is rubber a crystalline substance?

Amorphous solids, unlike crystalline solids, lack a structured inner structure. E.g., silicone, rubber, as well as gels. These solids, unlike crystalline substances with conventional cleavage planes, have identical physical properties in both directions.

4. Which solid is superior, crystalline/amorphous?

Amorphous is fundamentally less efficient than crystalline, with a light transmission effectiveness of just 7 to 10 percent compared to 12 to 15 percent for a crystalline panel of a similar size. Crystalline retains around 95 percent of the total of its indicated working performance during its lifespan.

5.Why are crystalline solids anisotropic & amorphous solids isotropic in nature?

Anisotropic crystals exhibit distinct physical properties, such as electrical resistance or refractive index, when measured in different orientations inside the identical crystal. Amorphous solids are isotropic due to their long-range order & irregular groupings.