In group 16 silicon dioxide is actually a very common compound that commonly happens as sand or quartz. SiO2 is tetrahedral with Each individual silicon atom surrounded by four oxygen atoms. Numerous crystalline forms exist With all the tetrahedra connected to sort a polymeric chain. Illustrations are tridymite and cristobalite. https://3d-printing59269.blogminds.com/alumina-crucible-can-be-fun-for-anyone-35649027