Which materials are described as having electrons that are free to move throughout the material?

Materials that are considered electrical conductors possess electrons that are free to move throughout the material. This characteristic is fundamental to their ability to conduct electricity. In conductors, particularly metals, the outermost electrons are loosely bound to the atoms, allowing them to drift freely when an electric field is applied. This movement of electrons is what constitutes an electric current.

In contrast, electrical insulators are materials in which electrons are tightly bound to their atoms, preventing them from moving freely. This lack of electron mobility means that insulators do not conduct electricity effectively.

Semiconductors have properties that fall between conductors and insulators. They can conduct electricity under certain conditions, mainly influenced by temperature or the addition of impurities, but do not have free-moving electrons to the same degree as conductors do.

Dielectrics are materials that do not conduct electricity but can support an electrostatic field, making them effective in capacitors and other electrical devices. They also lack significant numbers of free charges capable of movement.

Thus, the defining feature of conductors is the mobility of electrons, which allows them to facilitate electrical current efficiently.