(a) For an electrically nonconductive, extremely stiff, and lightweight material, classes to consider would be ceramics, polymers, and certain composite materials like fiber-reinforced composites.
(b) From a bonding perspective, each of these material classes possesses characteristics that align with the requirements.
1. **Ceramics**: These materials are known for their strong ionic or covalent bonding, resulting in a lack of free electrons, which makes them excellent insulators. Ceramics are often stiff due to their strong atomic/molecular bonds, and some, like certain types of advanced ceramics, can be lightweight.
2. **Polymers**: Typically, polymers have covalent bonds between their atoms, and the structure can be arranged in a way that doesn’t allow the free movement of electrons, making them good insulators. Polymers can be lightweight and, depending on the specific type, can also be quite stiff.
3. **Composite Materials**: Composite materials, particularly fiber-reinforced composites, combine properties of different materials. For instance, carbon fiber reinforced with a polymer matrix can offer excellent stiffness, lightweight characteristics, and insulating properties based on the combination of the fiber (often carbon) and the polymer matrix.
In summary, the selection of these material classes is due to their specific bonding properties that result in limited electron movement, thereby making them strong candidates for insulating, stiff, and lightweight applications.