Asymmetry of Si-O-Si bridge bond and atom groups in silicates

Analysis of silicon-oxygen distances and bond angles in simple silicates containing asymmetric bridge bonds Si-O...Si shows that the silicates with Si: O proportions of 1: 3, 1: 2.5, and 1: 2 are built of atom groups SiO ₃ ^2? , Si₂O ₅ ^2? , and SiO₂, respectively. The atoms in groups are linked through ordinary bonds Si-O or double bonds Si=O. The atoms of neighboring groups are linked by intergroup bonds Si...O which are longer than the ordinary bonds. The valences of the silicon and oxygen atoms are saturated on account of intragroup bonds; intergroup bonds are hypervalent. The structure of silicates is an analogue of the structure of compounds with intermolecular hydrogen bonds: in the latter, the atom valences are saturated by intramolecular bonds and intermolecular bonds are also hypervalent. In both cases, intergroup (intermolecular) bonds have the Coulombic nature