Why sio2 is solid and co2 gas

Covalent bonds are stronger than VDW. SiO2 is a network covalent solid. Each silicon makes four bonds by making four Si-O single bonds. The covalent network leads to a very strongly bonded solid with a very high melting point. The giant structures the metal oxides and silicon dioxide will have high melting and boiling points because a lot of energy is needed to break the strong bonds ionic or covalent operating in three dimensions.

These oxides tend to be gases, liquids or low melting point solids. Silicon has a very high melting point due to its giant covalent structure; a lot of energy is needed to break the strong covalent bonds throughout the structure. The key difference between SiO2 and CO2 is that the SiO2 exists in solid phase whereas, the CO2 exists in gaseous phase at standard temperature and pressure conditions.

SiO2 is silicon dioxide. CO2 is carbon dioxide. Both silicon and carbon are group 14 elements in the periodic table of elements. Only very weak dispersion intermolecular forces hold the molecules together and CO2 is a gas at room temperature.

Your email address will not be published. Save my name, email, and website in this browser for the next time I comment. Skip to content Every oxygen atom is bonded to two silicon atoms.

Does SiO2 have a low melting point? Is silicon dioxide a solid liquid or gas? Which is a molecular solid? It is a small molecule and non-polar with only weak bonds between the molecules. Hence it is a gas. Silicon dioxide is not formed of small molecules. It consists of an infinite array of silicons where each silicon is bonded to four separate oxygens and each oxygen is shared between two silicons.

This creates a strong refractory solid glass and sand are mostly silicon dioxide aka silica. So the same apparent overall formula doesn't describe the actual structure of the compounds at all. But the structures explain the difference in behaviour. Of course this doesn't explain why silicon prefers to bond with four oxygens when carbon prefers just two. This is not completely simple and results from the relative bond strengths of carbon-oxygen bonds, carbon-oxygen double bonds and the equivalent bonds for silicon and oxygen.

The simple version is that silicon oxygen bonds are strong relative to their double-bond equivalents whereas carbon-oxygen double bonds are strong relative to their single bond equivalents. Or, more precisely, if we could make a carbon-oxygen network solid with the equivalent structure to silica, it would tend to fall apart into carbon dioxide.

If we could make silicon dioxide molecules, they would react with the release of energy to give silica. Deeper explanations would need to look at why the relative strengths of double and single bonds turn out that way, but that would get into molecular quantum mechanics and would not be much more useful as an explanation. Also, the factor of 2.

I would recommend reading any inorganic chemistry book where such topics are discussed in depth. Van der Vaals forces only play significant roles in long-chain carbohydrates, such as fats, and are not really observed in "inorganic" molecules. Also, it has no dipole moment and no van der Waals forces between the molecules. Elements of the answer are also contained in other answers here but this needs some more teasing out. Sign up to join this community. The best answers are voted up and rise to the top.

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