Silicon

Figure 1. Silicon, atomic number of 14 and atomic weight of 28.0855.[1]

Silicon (Si) is the 14th element on the periodic table.[2] Silicon is the seventh most abundant element in the universe, and it is very common on Earth. In the Earth's crust, silicon is the second most abundant element. The most common compound of silicon is silicon dioxide, or SiO2. This compound is the most abundant compound in the Earth's crust, and it takes the form of ordinary sand, quartz, rock crystal, amethyst, agate, flint, jasper, and opal. Pure silicon is produced by heating silicon dioxide with carbon at temperatures approaching 2200°C.[2] Silicon can get quite pure, and even different isotopes can get quite pure. Special techniques are able to make silicon that is 99.9999% pure Si-28.[3]

Silicon is used extensively in electronics because of its semiconducting properties. As well, silicon is used extensively in the energy sector as the primary component of solar panels and photovoltaic cells. Silicon is used primarily in its solid form. It is also combined frequently with other elements to produce a number of useful products.

Some properties of silicon include:[4]

Atomic weight 28.0855
Density (at 0oC) 2.3296 g/cm3
Boiling point 3538 K
Melting point 1687 K
Embodied energy[5] 1000-1500 MJ/kg

Silicon is found in nature in the form of silicon dioxide (like some types of sand and many rocks). The extraction of silicon from silicon dioxide is extremely energy intensive; it requires 1000-1500 megajoules of primary energy per kilogram to process high-grade silicon for computer chips or solar cells.[6] This is an excellent example (along with aluminum) of a material that is limited far more by how much energy is needed to make the substance usable (embodied energy) than the abundance on the planet. In other words there will never be a shortage of silicon for any use that people have conceived of; the energy to process it will always be the limiting factor.

Uses

Since silicon has so many different forms that it appears in, it is very useful. When in the form of sand or clay, silicon can be used to make brick and other building materials. As a silicate, silicon is used for making enamels and pottery. Silica, another form of silicon, is the main ingredient in glass and can also be used in mechanical devices.[7]

Extremely pure silicon is useful as a semiconductor when doped with boron, gallium, phosphorus, or arsenic. This doped material is then used in diodes, transistors, and rectifiers. As well, this doped semiconducting material is the main component of photovoltaic cells, the cells that solar panels are made out of. The transistors created with this material can be used in microprocessor chips in computers and other advanced technologies.[7]

Additionally, silicon is an important ingredient in steel and silicon carbide is an extremely important abrasive.[7]

Video

The video below is from the University of Nottingham's periodic videos project.[8] They have created a complete suite of short videos on every element on the periodic table of elements.

References

  1. Made with information from the Royal Society of Chemistry, Available: http://www.rsc.org/periodic-table/element/14/silicon
  2. 2.0 2.1 Jefferson Lab. (August 25, 2015). Silicon [Online]. Available: http://education.jlab.org/itselemental/ele014.html
  3. See for example 'Beyond six nines: Ultra-enriched silicon paves the road to quantum computing' from phys.org, [online] http://phys.org/news/2014-08-nines-ultra-enriched-silicon-paves-road.html, accessed August 3rd, 2016.
  4. Royal Society of Chemistry. (August 25, 2015). Silicon [Online]. Available: http://www.rsc.org/periodic-table/element/14/silicon
  5. UNEP. (August 19, 2015). Environmental Risks and Challenges of Anthropogenic Metals Flows and Cycles [Online]. Available: https://d396qusza40orc.cloudfront.net/metals/3_Environmental_Challenges_Metals-Full%20Report_36dpi_130923.pdf#96
  6. UNEP. (August 31, 2015). Environmental Risks and Challenges of Anthropogenic Metals Flows and Cycles [Online]. Available: https://d396qusza40orc.cloudfront.net/metals/3_Environmental_Challenges_Metals-Full%20Report_36dpi_130923.pdf#96
  7. 7.0 7.1 7.2 Los Alamos National Laboratory. (August 25, 2015). Silicon [Online]. Available: http://periodic.lanl.gov/14.shtml
  8. See more videos from the University of Nottingham on different elements here: http://www.periodicvideos.com/

Authors and Editors

Gokul Dharan, Jordan Hanania, Kailyn Stenhouse, Jason Donev