Because of extremely small size of its atom and high electronegativity, boron differs in its properties from other elements of the group. On the other hand, it resembles silicon to some extent due to diagonal relationship. Boron and silicon exhibit the typical properties of nonmetals. These do not form cations. Both exist in amorphous as well as crystalline forms. Boron oxide ( ) and silica ( ) both are acidic and dissolve in alkali solutions to form borates and silicates respectively.