The vast majority of silicates are insoluble in water, except alkali metal silicate. The extreme stability is due to the donation of extra electrons from O atoms in to the vacant $3\mathrm{d}-\mathrm{orbital}$ of Si. The SiO₄ tetrahedral units may occur singly or may share one, two, three or four O atoms through comers giving rise to cycle groups, chains infinite layers of infinite three dimensions frame work