# Does SiO₂ have polar covalent bonds or coordinate covalent bonds?

First off, I know $\ce{SiO2}$ is a network solid. I am looking at its intramolecular forces between the $\ce{Si}$ and the $\ce{O}$ molecule. On the one hand, it seems to me that this should be a polar covalent bond, but on the other, both electrons are given to the $\ce O$ by $\ce{Si}$ which makes it coordinate covalent.

• As long as you think of molecules, you are dead wrong. There are no molecules. Jun 16 '17 at 18:42
• I'd never heard the term network solid before, thanks! It would certainly help in an answer to this question.
– uhoh
Jun 17 '17 at 0:19

Coordinate covalent bonds imply the donation of two electrons to a bond with another atom. In the case of $\ce{ SiO2 }$, The structure is actually tetrahedral, with an oxygen between and two silicon atoms, and where each oxygen forms two bonds and each silicon forms four bonds. In these bonds, each of the four valence electrons for silicon is shared singly with a single electron from one of the oxygens. Thus, in each bond, one of the electrons is from silicon and one from oxygen, which is why we don't normally consider this a coordinate covalent or dative bond.
This is one of those examples where the empirical formula, $\ce{ SiO2 }$, is highly misleading.
The $\ce{Si-O}$ bond has to be polar due to the difference in electronegativity of these atoms. However, due to the tetrahedral arrangement of these bonds, the net dipole moment should be zero.