Problem 48 - Introductory Chemistry Atoms First

Question

What is a network covalent substance? Give an example

Step-by-Step Solution

Answer

A network covalent substance is a chemical compound in which atoms are bonded via covalent bonds, forming a continuous and interconnected network structure. These substances have high melting and boiling points, are hard and rigid, and typically do not conduct electricity. An example of a network covalent substance is diamond, where carbon atoms are covalently bonded to form a strong tetrahedral lattice structure.

Step 1: Definition of Network Covalent Substance

A network covalent substance is a type of chemical compound in which the atoms are bonded to each other via covalent bonds, forming a continuous and interconnected network structure throughout the material. These substances are also known as covalent network solids.

Step 2: Characteristics of Network Covalent Substances

Some essential characteristics of network covalent substances are: 1. They have very high melting and boiling points because all the atoms within the structure are covalently bonded, requiring a large amount of energy to break these strong bonds. 2. These substances are typically hard and rigid due to the strong covalent bonding and continuous network structure. 3. They do not conduct electricity as they do not have free electrons available for the conduction of electric current. However, some network covalent substances like graphite can conduct electricity due to their unique structure, creating an exception. 4. Network covalent substances are generally insoluble in water and most other solvents.

Step 3: An Example of Network Covalent Substance

A commonly known example of a network covalent substance is Diamond (a form of Carbon). In a diamond, each carbon atom is covalently bonded to four other carbon atoms, forming a strong tetrahedral lattice structure throughout the material. This interconnected network of carbon atoms via covalent bonds gives diamond its remarkable hardness and high melting point.

Key Concepts

Covalent Bonds

Simply put, covalent bonds are the 'glue' that holds atoms together within a molecule. They are formed when atoms share pairs of electrons, allowing each atom to achieve a full outer shell, which is a state of stability according to the octet rule. Take water (H2O) as an example; it consists of hydrogen and oxygen atoms bonded together covalently, with the oxygen atom sharing its electrons with the hydrogen atoms.

Unlike ionic bonds, which are formed between oppositely charged ions, covalent bonds form between atoms that have similar electronegativities. This means that the atoms involved in a covalent bond typically pull on the shared electrons with similar strength, resulting in a reliable and stable bond. The strength of a covalent bond contributes to a substance's melting point, boiling point, and its overall stability.

Chemical Compound

Broadly speaking, a chemical compound is a substance formed from two or more different elements that are bonded together chemically. Each element within the compound loses its individual properties to give way to new properties. For instance, sodium is a reactive metal and chlorine is a dangerous gas, but when they form sodium chloride (table salt), the compound is completely safe for consumption.

To be clear, the key to a compound is not just the physical mix of elements, but the chemical bonding that merges them into a unit with unique characteristics. Compounds can be broken back down into their constituent elements, but it requires a chemical reaction, sometimes simple, often complex, to disrupt those stable bonds.

Properties of Network Covalent Substances

Network covalent substances are fascinating due to their distinct attributes. They are iconic for having extraordinarily high melting and boiling points. This is because every atom is bonded tightly to its neighbors with covalent bonds, demanding massive amounts of energy to break these connections. The robust structure of network covalent substances also means they are not just strong, but also extremely hard and rigid.

When it comes to electrical conductivity, these substances generally do not conduct electricity, lacking the free-moving electrons needed for electron flow. However, a few, like graphite, make for notable exceptions due to their unique structural attributes. Another commonality among these substances is their insolubility in water and most solvents; because their atoms are interlinked so firmly, there's little opportunity for solvents to penetrate and dissolve the substance.

Example of Network Covalent Substance

Diamond is the poster child for network covalent substances. It is more than just a symbol of commitment; it's a masterclass in atomic architecture. Each carbon atom in a diamond is bonded to four others, creating an endlessly repeating tetrahedral pattern that extends throughout the entire structure. This uniform and unyielding lattice awards diamond its hardness, which is unparalleled in the natural world.

Beyond its durability and sparkling allure, diamond's network covalent structure imparts high thermal conductivity while also making it an electrical insulator. Such a juxtaposition of properties makes diamonds not only a gemstone but also a material of great interest for industrial applications, including cutting and heat dissipation in electronics.