What two elements widely used in semiconductor devices exhibit both metallic and non-metallic characteristics?

Silicon and germanium are elements known as metalloids, meaning they exhibit properties of both metals and non-metals. This unique dual nature is what allows them to act as semiconductors, making them the foundational materials for modern solid-state electronics like diodes and transistors. Because they have exactly four valence electrons in their outer shell, they can form perfect crystal lattices. By introducing specific impurities in a process called doping, engineers can precisely control their electrical conductivity. Other options are incorrect because gold is purely a metal and an excellent conductor. Galena (lead sulfide) is a chemical compound rather than a fundamental element, even though it was historically used in early crystal radio sets.