<P> Boron has many carbon - like properties, but is very rare . It has many uses, for example a P type semiconductor dopant . </P> <P> Silicon is perhaps the most famous metalloid . It is the second most abundant element in Earth's crust and one of the main ingredients in glass . It is used to make semiconductor circuits, from large power switches and high current diodes to microchips for computers and other electronic devices . It is also used in certain metallic alloys, e.g. to improve casting properties of alumimium . So valuable is silicon to the technology industry that Silicon Valley in California is named after it . </P> <P> Germanium has properties very similar to silicon, yet this element is much more rare . It was once used for its semiconductor properties pretty much as silicon is now, and it has some superior properties at that, but is now a rare material in the industry . </P> <P> Arsenic is a toxic metalloid that has been used throughout history as an additive to metal alloys, paints, and even makeup . </P>

The periodic table consists of four blocks of elements