Classification of Solids: Molecular, Ionic, Covalent and Metallic Solids

The matter is categorized into three types based on its physical properties.

1. Solid
2. Liquids
3. Gas

We will learn about solids and their properties in this section. The topic of solids and their classification is very important in chemistry. Because the molecules of solid substances are densely packed, solids have a specific volume and a particular form. The molecules of solid substances remain so close to each other that there is no space between them.

What is solid?

Solids have a regular arrangement of atoms, molecules, or ions in a kinetic molecular model. Because these particles are held close together by relatively strong forces of attraction, solid particles are packed in proper order or symmetry. They maintain a fixed position in the substance, so they have a definite shape, a distinct boundary, a fixed volume, and negligible compressibility. Some solids are very strong, while others can be broken by force. A solid’s qualities are determined by its nature and the arrangement of its molecules.

Examples-, glass, table sugar, water ice, table salt, frozen carbon dioxide (dry ice),  rock, most metals, and wood.

Characteristics of solid

Let’s look at some of the distinct characteristics of solids.

Every material has certain qualities. The major qualities of solid substances are as follows:

1.  They have defined mass, volume, and form due to strong intermolecular attraction forces.
2. They have precise limits.
3. They have a predetermined volume.
4. They are unable to flow.
5.  They have slight compressibility since the distance between neighboring molecules is negligible.
6. They are stiff and tend to maintain their form when subjected to external stress.
7. Some solids may shatter with force, but changing their form is difficult.

They are very dense and do not disperse at all.

Classification of solids

There are many classifications of solid substances all around us. Whatever we see around us in real life, most of them are solid. Every solid substance in the world is classified into two types. They are as follows: 1. crystalline solid and 2. amorphous solid.

Let’s go over this in detail.

1. Solid crystalline

The structures and symmetry of crystalline solids or crystals are organized. Because the atoms, molecules, or ions in a crystal are ordered in a certain way, the arrangement should have long-range order in the solid. Look at the image below. The particles (atoms, molecules, and ions) exhibit long-range order in the crystalline solid material. The component atoms, molecules, or ions of crystalline materials form a regular, repeating pattern (i.e. particles in the solid substance). They lack well-defined particles because they lack regular particle configurations. A crystalline solid is a three-dimensional periodic arrangement of atoms, ions, or molecules that results in a well-defined geometric structure.

The atoms or molecules in a solid acquire kinetic energy when heated. If the temperature rises enough, the kinetic energy exceeds the forces that keep the atoms or molecules together. The solid may then transform into a liquid or a gas or react with substances in the surroundings. Water ice is an example of a solid that turns liquid when gradually heated. Dry ice sublimates into the gaseous phase. Wood reacts with oxygen in the environment, causing it to burn.

What exactly is a crystal?

A crystal, according to definition, is “a homogeneous chemical substance having a regular and periodic arrangement of component atoms, molecules, or ions.”

Salt (NaCl) and quartz are two examples (SiO2).

Many people believe that crystals can only be found in minerals. However, you will be shocked to learn that crystals are not limited to minerals. Most solid substances that are not a mineral, such as sugar, diamonds, metals, bones, and even DNA, form a crystal.

Crystals are classified as follows:

Crystals are solid objects. The crystals may be classified in a variety of ways. We will explore the categories based on their physical and chemical features in this section (i.e. types of bonds present in the solid). There are four types of crystals: covalent crystals, metallic crystals, ionic crystals, and molecular crystals e.g Calcium chloride,diamond etc

Covalent crystals are made up of atoms that are covalently bound to one another. Silicon carbide, for example, or diamond

Metallic crystals are made up of atoms joined together by the metallic bond. Consider the mineral pyrite.

Ionic crystals are made up of atoms or ions bound together by the Ionic bond. Calcium chloride is one example.

Molecular crystals are a kind of crystal. This crystal relies only on molecules to keep other molecules together through the Van Der Waals force. As a result, this form of crystal has a low intermolecular binding. As an example, consider sugar and dry ice.

Crystals come in a variety of forms and hues. Crystals have an aesthetic value and are thought to have therapeutic qualities; hence, they are used to produce jewelry.

2. Amorphous Substance

Now we’ll look at another kind of solid material. It is referred to as an amorphous solid. An amorphous solid lacks a crystalline structure, which implies it lacks a long-range regular and periodic arrangement of component atoms, molecules, or ions (i.e. particles of the solid). It signifies that the structure lacks a long-range organized arrangement of component atoms, molecules, or ions. As a result, we may describe it as a powder-like solid material. Examples- glass, gels, thin films, polymers, and nanostructured materials.

Molecular solids

A molecular solid is a solid made up of molecules kept together by van der Waals forces. Molecular solids are soft and have a low melting point because dipole forces are less than covalent or ionic interactions. Molecular solids are classified into three types:

• Non-polar molecular solids: The atoms or molecules of non-polar Molecular solids are held together by weak dispersion forces or London forces. They are soft and do not conduct electricity. They have low melting points and are usually liquids or gasses at ambient temperature and pressure. Example- Carbon tetrachloride
• Polar Molecular solids: These are solids with polar molecules as component particles. The molecules are held together by dipole-dipole attraction. They are supple and non-conductors of electricity. Example- Solid CO2, Solid NH3

Conclusion

Some chemicals create crystalline solids, which are made up of particles in a fairly structured structure, whereas others from amorphous (noncrystalline) solids, which have an unorganized internal structure. Ionic solids, metallic solids, covalent network solids, and molecular solids are the four basic forms of crystalline solids. The characteristics of various crystalline solids are determined by the particles that comprise them, the configurations of the particles, and the intensities of the attractions between them. Because their particles experience similar attractions, crystalline solids have unique melting temperatures; amorphous solids soften gradually and melt across a range of temperatures because their particles experience a variety of interactions.