What is Silicon? - Properties & Uses

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  • 0:00 Supply And Demand
  • 1:05 Defining Silicon
  • 2:27 Silicon's Multitude Of Uses
  • 6:00 Lesson Summary
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Lesson Transcript
Instructor: Scott van Tonningen

Scott has a Ph.D. in electrical engineering and has taught a variety of college-level engineering, math and science courses.

Learn more about silicon and its amazing qualities. It is one of the most abundant materials on Earth and has a myriad of uses. After the lesson, a quiz is provided to check your understanding.

Supply and Demand

It seems like everywhere you turn nowadays there are shortages. There are water, food, and drug shortages. There are shortages of skilled nurses. There are critical shortages of the rare earth elements we need in hybrid cars, wind turbines, and TV displays. And, whenever there is a shortage of something that is in high demand, the costs go up. In 2014, gasoline prices at the pump had increased nearly 1400% over the previous 40 years. In the same four decades, nursing salaries rose 1200%. And, I don't have to tell you what has happened with food costs. Thank goodness silicon, one of the most important things we need, is also one of the most abundant resources on the planet.

Next time you are at the beach or the sand dunes, pick up a handful of sand. About half the weight of the sand you're holding is silicon. In fact, silicon is the second most common element on the planet Earth. Almost 28% of the earth's crust is made up of silicon. Let's find out more about this very abundant, very useful, and very inexpensive element.

Defining Silicon

Silicon (Si) is one of seven elements that are known as the metalloids. This is just a fancy term to describe certain elements that don't behave exactly like metals or exactly like non-metals. The generally accepted list of metalloids is silicon, germanium, boron, arsenic, antimony, tellurium, and polonium. Silicon can have properties like a metal or a non-metal depending on what other elements it combines with. Glass is a very common silicon compound that has non-metal qualities, while the silicon used in electronics can be made to act very much like a metal.

Silicon is similar to carbon. You probably know that carbon is the main ingredient in pencil lead (or graphite) or in diamonds. Carbon combines with a huge number of other elements, and every compound has different properties. This is the way it is with silicon.

At the atomic level, silicon has 14 electrons, 4 of which are in the outer shell (the highest energy level), and it bonds readily with other elements. Silicon occurs in nature primarily as silicon dioxide, which is also called silica. It's found in sand, quartz, agate, and even opal. Silica is by far the most common compound found naturally on Earth. This picture shows the silicon atom and the combination of silicon and oxygen atoms that make up silica. This is the lattice structure that makes up quartz (see video).

Silicon's Multitude of Uses

So what are some uses for silicon?

One of the most important properties of silicon is that it's a semiconductor, meaning its ability to conduct electricity is better than an insulator (like sulfur) but not as good as a conductor (like copper). When pure silicon is infused with other elements (called impurities) such as boron or phosphorous, the number of available electrons in the mix changes. This process is called doping.

Through the use of doping and the creation of junctions between differently doped silicon regions, nearly any electronic circuit component can be produced from silicon on an integrated circuit (or IC) chip. This includes diodes, transistors, resistors, capacitors, insulators, and even highly conducting paths that can replace expensive metals such as gold. IC chips are produced on a round wafer of silicon, such as the one pictured here (see video).

Silicon dioxide is the main ingredient of glass. Glass is made by melting silicon sand (also called quartz sand) with carbon at a high temperature (up to 4000 degrees Fahrenheit). When the glass forms, the mixture releases the carbon and oxygen as a gas (carbon monoxide). Glass has been around for thousands of years; the earliest known manufacture of glass was in 2000 B.C.E. in Mesopotamia (now Iraq).

Silicon can also take the form of silicon carbide. This combination of silicon and carbon has been in production since the 19th century. It is virtually indestructible, almost as hard as diamond, and can withstand the highest temperatures without melting. It is used in numerous industrial applications, including abrasives, grinding, polishing, cutting, kilns, body armor, and the aerospace industry.

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