Silicates as the base of the Earth crust
Silica and compounds derived from it, silicates, constituteca. `90%` of the Earth crust substances. Silica gives rise to a beautiful meterial-glass. Nobody knows exactly how glass was discovered. There is a well-favoured story related to phoenician sailors who fused occassionally sea sand and soda ash. It is likely that they discovered the secret of "liquid glass" `(LGL)` sodium metasilicate `(Na_(2)SiO_(3))` soluble in water.
Determine the number of oxygen atoms bridging adjacent tetrahedra.