Nonmetal inconsistently classified by different authors. Elements sometimes also classified as nonmetals are the metalloids boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te), and astatine (At). The nonmetal selenium (Se) is sometimes instead classified as a metalloid, particularly in environmental chemistry. Nonmetals show more variability in their properties than do metals. These properties are largely determined by the interatomic bonding strengths and molecular structures of the nonmetals involved, both of which are subject to variation as the number of valence electrons in each nonmetal varies. Metals, in contrast, have more homogenous structures and their properties are more
Binary compounds of silicon practical applications), formed by annealing an amorphous Si-P alloy. The arsenic–silicon phase diagram measured at 40 Bar has two phases: SiAs and SiAs. The antimony–silicon system comprises a single eutectic close to the melting point of Sb. The bismuth system is a monotectic. In group 16 silicon dioxide is a very common compound that widely occurs as sand or quartz. SiO is tetrahedral with each silicon atom surrounded by 4 oxygen atoms. Numerous crystalline forms exist with the tetrahedra linked to form a polymeric chain. Examples are tridymite and cristobalite. A less common oxide is silicon monoxide that can be