In group 16 silicon dioxide can be a quite common compound that commonly takes place as sand or quartz. SiO2 is tetrahedral with each silicon atom surrounded by 4 oxygen atoms. Many crystalline kinds exist While using the tetrahedra associated with type a polymeric chain. Examples are tridymite and cristobalite. https://metal3dprintingservice60369.uzblog.net/an-unbiased-view-of-bismuth-oxide-52409378