Question

Classify each of the following as a conductor, an insulator, or a semiconductor: (a) carbon (graphite); (b) sulfur; (c) platinum.

Short answer

Carbon (graphite) is a conductor, sulfur is an insulator, and platinum is a conductor.

Step-by-step solution

Basics of Conductors, Insulators, and Semiconductors

Understand the definitions. Conductors allow electric current to flow easily (many free electrons). Insulators resist electric current (few free electrons). Semiconductors have electrical properties intermediate between conductors and insulators and can conduct electricity under certain conditions.

Classify Carbon (Graphite)

Graphite is a form of carbon where each carbon atom is bonded to three other carbon atoms, forming layers. These layers can slide over each other easily and contain free electrons. Therefore, graphite can conduct electricity. Thus, carbon (graphite) is a conductor.

Classify Sulfur

Sulfur is a non-metal and has a crystalline structure with covalent bonds holding the atoms together. This structure creates very few free electrons to conduct electricity. Therefore, sulfur is an insulator.

Classify Platinum

Platinum is a metal with free electrons that can move easily through its atomic structure, allowing it to conduct electric current very efficiently. Therefore, platinum is a conductor.

Key concepts

Conductors

Conductors are materials that allow electric current to flow through them easily. This happens because they have a large number of free electrons. These free electrons can move around inside the material, carrying the electric current. Metals like copper, aluminum, and platinum are good examples of conductors.
When we say a material is a conductor, it's mainly because of the way its atoms are structured. In conductors, the outer electrons of the atoms can move freely. This freedom of movement is what allows electricity to flow.
If we take graphite (a form of carbon) as an example, it's a conductor. In graphite, each carbon atom forms bonds with three other carbon atoms in flat layers. These layers can slide over each other, and the free electrons between the layers are what make graphite conductive.
Some properties of conductors are:

• High electrical conductivity
• Free electrons available
• Metals typically have good conductivity

Insulators

Insulators are materials that do not allow electric current to flow through them easily. This is because they have very few free electrons. Instead, the electrons in insulators are tightly bound to their atoms and cannot move freely.
Materials like rubber, glass, and sulfur are excellent examples of insulators. For instance, sulfur is an insulator because of its crystalline structure. In sulfur, the atoms are held together with covalent bonds. These bonds do not leave free electrons available to conduct electricity.
When measuring the conductivity of an insulator, you'll find that it is very low compared to conductors. This makes insulators very useful for protecting against electrical shocks and for coating electrical wires.
Key properties of insulators include:

• Low electrical conductivity
• Few or no free electrons
• Used to prevent the flow of electric current

Semiconductors

Semiconductors have properties that are between those of conductors and insulators. They can conduct electricity, but not as well as conductors. However, their ability to conduct electricity can be controlled under certain conditions, such as by adding impurities (a process called 'doping') or by changing the temperature.
Common examples of semiconductors are silicon and germanium. These materials are critical in the manufacturing of electronic devices like diodes, transistors, and integrated circuits. In a semiconductor, the electrons are not as free to move as in a conductor, but they are also not tightly bound as in an insulator.
The unique property that allows semiconductors to switch between conducting and non-conducting states makes them very useful in electronic circuits. By applying a small voltage, we can control the flow of a larger current, which is the basis of how a transistor works.
Characteristics of semiconductors include:

• Intermediate electrical conductivity
• Conductivity can be modified
• Essential in modern electronics