# 6.11F: Structure - $$\beta$$-Cristobalite $$SiO_2$$

Silicon dioxide, SiO2, also known as silica is a linear molecule that is formed by one silicon atom and two oxygen atoms with two sets of doubles bonds and 4 single bonds. Because of its main component: glass, silicon dioxide is a very common and important molecule in the construction industry. One of the forms of silicon dioxide is quartz, which is found in sand.

### The Structure of SiO2

SiO2 is a 3 dimensional structure and comes from the tetrahedral structure, SiO4. Each of the Silicon atoms are connected to each other with an oxygen atom, which creates a "diamond type network". All forms of SiO2 possess a 3 dimensional shape and has a diamond structure. The bonding angle of Si-O-Si, which is the building block of the SiO2 molecule, is 144 degrees. These are called polymorph and in order to be stable, 3 of these polymorph are suppose to exist. This stable unit creates a a temperature for each of the different forms of SiO2. Forms that have (alpha) are at low temperature, while forms with (beta) are at high temperature. The structure of the different forms of SiO2 is important because it gives each of the different forms of SiO2 different characteristics and functions. Commercially, SiO2 is very important in steel, electronic, and semiconductor industries because of its structure, SiO2 is able to undergo rapid temperature changes and still maintain its shape and structure.

### Different Forms of SiO2and Their Uses

There are many different forms of SiO2, which mainly derived quartz glass. One form that is derived from quartz is beta-cristobalite, which is found in high temperature. Some other forms are beta-quartz, alpha-quartz, beta-tridymite, alpha-tridymite, alpha=cristobalite, and many more. The alpha and beta stands for the temperature range. Alpha molecules have low temperature while beta molecules have high temperature.

References

1. Ed. Papier, Eugene. 2000. Absorption on Silica Surfaces. Marcek Dekker. New York.
2. Pacific Rim Conference on Ceramic and Glass Technology. 2006. Advances in Glass and Optical Materials II. American Ceramic Society. Westerville, Ohio.
3. Housecroft, Catherine E., and Alan G. Sharpe. 2008. Inorganic Chemistry. 3rd ed. Harlow: Pearson Education.

### Problems

1. What kind of structure does SiO2 formed?

A. SiO2 has a "diamond type network" structure, that formed because of how the Si-O-Si is linked together.

2. What are the uses for SiO2

A. It is largely use in the construction industry because of its stability.

3. Why is SiO2 stable?

A. SiO2 can undergo rapid temperature change, which makes the molecule stable and therefore it can remain its shape and structure.

### Contributors

• Name #1 here (if anonymous, you can avoid this) with university affiliation