Metalloids
Metalloids sit at the diagonal boundary between metals and non-metals. They combine partial conductivity and brittleness, making them the raw material of all modern electronics.
Boron, silicon, germanium, arsenic, antimony, tellurium: this heterogeneous family shares one essential feature — semiconductor properties tunable by doping. Silicon is the physical substrate of all contemporary microelectronics; germanium preceded silicon in the first transistors and is still used in infrared optics.
Arsenic and antimony have a long toxicological and medical history (salvarsan, alchemy, pigments). Boron is essential to glass chemistry (borosilicate) and plant biology.
Electronically, metalloids have a moderate band gap: neither metallic conductors nor pure insulators. This is the property that enables transistors and photovoltaic cells.