I was studying about the hydrolysis and i saw an example in my book showing the hydrolysis of the compounds having vacant d-orbitals. In the example, hydrolysis of SiCl4 is shown. SiCl4 is attacked by water molecules and produce H4SiO4 and 4HCl. Then it is written that H4SiO4 is unstable and forms H2SiO3 and H2O. Can somebody explain me why H4SiO4 is unstable? Any help is much appreciated. Thanks!