SILICON





Silicon 3311
Photo by: marema

Silicon

Overview

Silicon is a member of Group 14 (IVA) in the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. Silicon is also part of the the carbon family. Other carbon family elements include carbon, germanium, tin, and lead. Silicon is a metalloid, one of only a very few elements that have characteristics of both metals and non-metals.

Silicon is the second most abundant element in the Earth's crust, exceeded only by oxygen. Many rocks and minerals contain silicon. Examples include sand, quartz, clays, flint, amethyst, opal, mica, feldspar, garnet, tourmaline, asbestos, talc, zircon, emerald, and aquamarine. Silicon never occurs as a free element. It is always combined with one or more other elements as a compound.

SYMBOL
Si

ATOMIC NUMBER
14

ATOMIC MASS
28.0855

FAMILY
Group 14 (IVA)
Carbon

PRONUNCIATION
SIL-i-con

By the early 1800s, silicon was recognized as an element. But chemists had serious problems preparing pure silicon because it bonds (attaches) tightly to oxygen. It took chemists many years to find out how to separate silicon from oxygen. That task was finally accomplished in 1823 by Swedish chemist Jons Jakob Berzelius (1779-1848).

Silicon's most important application is in electronic equipment. Silicon is one of the best materials from which to make transistors and computer chips. The total weight of silicon used for this purpose is relatively small. Much larger amounts are used, for example, to make metal alloys. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals.

Discovery and naming

In one sense, humans have always used silicon. Nearly every naturally occurring rock or mineral contains some silicon. So when ancient peoples built clay huts or sandstone temples, they were using compounds of silicon.

But no one thought about silicon as an element until the nineteenth century. Then, a number of chemists tried to separate silicon from the other elements with which it is combined in the earth. English scientist Sir Humphry Davy (1778-1829) developed a technique for separating elements that tightly bond to each other. He melted these compounds and passed an electric current through them. The technique was successful for producing free or elemental sodium, potassium, calcium, and a number of other elements for the first time. But he failed with silicon. (See sidebar on Davy in the calcium entry in Volume 1.)

Berzelius also tried to isolate silicon using a method similar to that of Davy's. He mixed molten (melted) potassium metal with a compound known as potassium silicon fluoride (K 2 SiF 6 ). The result was a new element—silicon.

Scottish chemist Thomas Thomson (1773-1852) suggested the name silicon, based on the Latin word for "flint," silex (or silids). He added the ending -on because the new element was so much like boron and carbon. Thus, the new element's name was accepted as silicon.

Some interesting studies were done on silicon over the next few years. German chemist Friedrich Wohler (1800-82) produced a series of compounds known as silanes. These compounds contain silicon, hydrogen, and, sometimes, other elements.

Purified silicon bar.
Purified silicon bar.
The simplest silane is silicon tetrahydride (SiH 4 ). This compound is also called silane.

A group of compounds known as the siloxanes were produced at about the same time. The siloxanes are made up of silicon, oxygen, and an organic group. Organic compounds contain carbon.

Silanes and siloxanes were not discovered in the search for the answer to any practical question. Chemists were just curious about the kinds of compounds they could make with silicon. But many years later, chemists made some interesting discoveries. Both groups of compounds do have some very important practical uses. For example, the compounds known as silicones are a form of the siloxanes.

Physical properties

Silicon is a metalloid, an element with properties of both metals and non-metals. Silicon exists in two allotropic forms. Allotropes are forms of an element with different physical and chemical properties. One allotrope is in the form of shiny, grayish-black, needle-like crystals, or flat plates. The second allotrope has no crystal structure and usually occurs as a brown powder.

The melting point of silicon is 1,410°C (2,570°F) and the boiling point is 2,355°F (4,270°F). Its density is 2.33 grams per cubic centimeter. Silicon has a hardness of about 7 on the Mohs scale. The Mohs scale is a way of expressing the hardness of a material. It runs from 0 (for talc) to 10 (for diamond).

Silicon is a semiconductor. A semiconductor is a substance that conducts an electric current better than a non-conductor—like glass or rubber—but not as well as a conductor—like copper or aluminum. Semiconductors have important applications in the electronics industry.

Chemical properties

Silicon is a relatively inactive element at room temperature. It does not combine with oxygen or most other elements. Water, steam, and most acids have very little affect on the element. At higher temperatures, however, silicon becomes much more reactive. In the molten (melted) state, for example, it combines with oxygen, nitrogen, sulfur, phosphorus, and other elements. It also forms a number of alloys very easily in the molten state.

Occurrence in nature

Silicon is the second must abundant element in the Earth's crust. Its abundance is estimated to be about 27.6 percent of the crust. It ranks second only to oxygen. Some authorities believe that more than 97 percent of the crust is made of rocks that contain compounds of silicon and oxygen.

Silicon has been detected in the Sun and stars. It also occurs in certain types of meteorites known as aerolites or "stony meteorites." Meteorites are rock-like chunks that fall to the Earth's surface from outside the Earth's atmosphere.

Silicon never occurs as a free element in nature. It always occurs as a compound with oxygen, magnesium, calcium, phosphorus, or other elements. The most common minerals are those that contain silicon dioxide in one form or another. These are known as silicates.

Silicon has been detected in the Sun and stars. It also occurs in certain types of meteorites.

Isotopes

There are three naturally occurring isotopes of silicon: silicon-28, silicon-29, and silicon-30. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope.

Five radioactive isotopes of silicon are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive.

None of the radioactive isotopes of silicon has any commercial use.

Extraction

Silicon is prepared by heating silicon dioxide with carbon. Carbon replaces the silicon in the compound. The silicon formed is 96 to 98 percent pure.

Many applications of silicon require a very pure product. Methods have been developed to produce silicon that is at least 99.97 percent pure silicon. This form of silicon is called hyper-pure silicon.

Uses

Perhaps the best known use of silicon is in electronic devices. Hyperpure silicon is used in transistors and other components of electronic devices. It is also used to make photovoltaic (solar) cells, rectifiers, and parts for computer circuits. A photovoltaic cell is a device that converts sunlight into electrical energy. A rectifier is an electrical device for changing one kind of electric current (alternating current, or AC) into another kind of electric current (direct current, or DC).

Almost without exception, all glass contains silicon dioxide.

The largest single use of silicon, however, is in making alloys. The most important silicon alloys are those made with iron and steel, aluminum, and copper. When silicon is produced, in fact, scrap iron and metal is sometimes added to the furnace. As soon as the silicon is produced, it reacts with iron and steel to form ferrosilicon. Ferrosilicon is an alloy of iron or steel and silicon. It is used for two major purposes. First, it can be

A circular wafer of silicon carrying many individual integrated circuits.
A circular wafer of silicon carrying many individual integrated circuits.
added to steel to improve the strength and toughness of the steel. Second, it can be added during the steel-making process to remove impurities from the steel that is being made.

The aluminum industry uses large amounts of silicon in alloys. These alloys are used to make molds and in the process of welding. Welding is a process by which two metals are joined to each other. Alloys of silicon, aluminum, and magnesium are very resistant to corrosion (rusting). They are often used in the construction of large buildings, bridges, and transportation vehicles such as ships and trains.

Compounds

A number of silicon compounds have important uses. Silicon dioxide (sand) is used in the manufacture of glass, ceramics, abrasives, as a food additive, in water filtration systems, as an insulating material, in cosmetics and Pharmaceuticals (drugs), and in the manufacture of paper, rubber, and insecticides. Each

A wire bonded to a silicon chip that houses an integrated circuit. The photo is magnified 280 times.
A wire bonded to a silicon chip that houses an integrated circuit. The photo is magnified 280 times.
of these applications could be the subject of a very long discussion in and of itself. For example, humans have made glass for thousands of years. Today, dozens of different kinds of glass are produced, each with special properties and uses. But almost without exception, they all contain silicon dioxide.

Another important compound is silicon carbide (SiC). Silicon carbide is also known as carborundum. It is one of the hardest substances known, with a hardness of about 9.5 on the Mohs scale. Carborundum is widely used as an abrasive, a powdery material used to grind or polish other materials. Carborundum also has refractory properties. A refractory material can withstand very high temperatures by reflecting heat. Refractory materials are used to line the inside of ovens used to maintain very high temperatures.

Another important silicon group is the silicones. The silicones have an amazing range of uses. These include toys (Silly Putty and Superballs), lubricants, weatherproof!ng materials, adhesives (glues), foaming agents, brake fluids, cosmetics, polishing agents, electrical insulation, materials to reduce vibration, shields for sensitive equipment, surgical implants, and parts for automobile engines.

Health effects

Information on the health effects of silicon is limited. Some studies show that silicon may be needed in very small amounts by plants and some animals. One study showed, for example, that chickens that did not receive silicon in their diet developed minor health problems. Overall, silicon probably has no positive or negative effects on human health.

However, a serious health problem called silicosis is associated with silicon dioxide (SiO 2 ). Silicon dioxide occurs in many forms in the earth. Ordinary sand is nearly pure silicon dioxide.

In some industries, sand is ground up into a very fine powder that gets into the air. As workers inhale the dust, it travels through their mouths, down their throats, and into their lungs. Silicon dioxide powder can block the tiny air passages in the lungs through which oxygen and carbon dioxide pass. When this happens, silicosis results.

Silicosis is similar to pneumonia. The person finds it difficult to breathe. The longer one is exposed to silicon dioxide dust, the worst the problem gets. In the worst cases, silicosis results in death because of the inability to breathe properly.



User Contributions:

Demi-Jessica
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Nov 6, 2007 @ 5:17 pm
Thank you so very much this really helped me out with my chemistry project, please keep up the good work. This gave very precise information just what I needed.

Until next time
Demi.
Adina
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Nov 20, 2007 @ 2:14 pm
I am working on a chemistry project on Si, and this website helped so much! Thank you!!!
shannon
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Mar 12, 2008 @ 6:18 pm
this was realy good info for my science project,Clear,understandable and easy to read

this is great info. Keep it up guys!
Christine
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Mar 17, 2008 @ 8:08 am
Very easy to understand, clear and precise. Helped me on my chemistry homework.
Thanks!
Mel DECV! :)
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May 20, 2008 @ 9:21 pm
thanks guys. this realy realy helped with my project im doing on metalliods! :)
chaio! x
mel
llya
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Jun 26, 2008 @ 9:09 am
thank you so much for this information,, the uses of each elements is what i really really need.. god bless!
keasha
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Dec 22, 2008 @ 3:03 am
dis really a great help 2 all students especially or me....
thank u so much....gOd bless
Robyn
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Sep 14, 2009 @ 2:14 pm
Thank you so much, this was fantastic for my chemistry homework! Keep it up!
Annie
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Nov 2, 2009 @ 6:18 pm
Thank you so much for your website. I'm doing a science project and your website has helped me find over half of my imformation! You are making my job a whole lot easier. Thanks :)
Ansley
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Dec 1, 2009 @ 9:09 am
Thanks for the info it helped me study for a test keep up the good work
pimps
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Dec 17, 2009 @ 10:22 pm
thanx alot for helping me coulldntdo it with out u guys
liz
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Dec 29, 2009 @ 3:15 pm
thanx for the great info it really helped me with my science project!!!
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Feb 17, 2010 @ 8:08 am
This information was very helpful. I have been researching silicon and have found information showing that it is very helpful for the health of humans as Diatomaceous earth. I would to see what your thoughts are on this topic.
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Mar 29, 2010 @ 5:17 pm
Thank you so much whoever wrote this. This is an amazing site! I am doing a project on silicon and I'm presenting it to my classmates. Thanks again!
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May 5, 2010 @ 9:21 pm
We need teachers who can explain something in this simple way to a student
who ever explained this is a very good teacher/professor. THANKS!
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May 24, 2010 @ 10:22 pm
Thank you so much for the info! It really helped me out with my Science project! I have to make a 3D Model of a Silicon Atom and this helped alot. Thanks!!!
Jupiter Guy
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Jun 1, 2010 @ 10:10 am
Thanks for the great info on silicon in humans it helped me with my science project on Jupiters gasses
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Jun 10, 2010 @ 6:06 am
How do resistant silicone or a substance like silicon?
Dear friends. How can I make it more durable silicone molds? How do I make a substance like silicon? Instead of silicon we do want to use a substance. How to make this item? Rates and do not know which substances to be used. I appreciate if you can help me with this.
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Sep 11, 2010 @ 6:18 pm
This sight helped me so much on my Silicon project!
Thanks!
angel
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Sep 25, 2010 @ 9:21 pm
thanks. good info for project on silicon. i thought it was just breaast implants:)
Emma
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Oct 17, 2010 @ 8:20 pm
Thank you so much!
I used this article for a school project and need to cite it.
Who is the author?
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Oct 20, 2010 @ 4:16 pm
thanks u very very much.this is very precise and acccurate it really really helped me .keep up your good work
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Oct 28, 2010 @ 7:19 pm
Thank You so much, you basically answered 90% of the questions I needed to answer on my report. :)
Alex Melberg
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Nov 4, 2010 @ 7:19 pm
This article was very interesting and useful to me, because I have to do a project on this element for my chemistry class in high school.
usama
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Nov 6, 2010 @ 7:19 pm
How is the elements and its compounds used by humans?
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Nov 9, 2010 @ 8:20 pm
That's pretty awesome! Thanks! I just worked on my Chemistry project and it helped me a lot. Easy to read and interesting. Thanks!
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Dec 1, 2010 @ 7:19 pm
This is great I just filled out my fact sheet, but mabey telling were it was discovered
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Dec 8, 2010 @ 11:23 pm
Thank you so much this helped me a lot with a science project and it is easy to read and very well explained.
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Jan 5, 2011 @ 9:09 am
This was very helpful for my science project. The information covered every possible category that I needed to talk about in my presentation. Thank you!
gurrll! ;)
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Jan 18, 2011 @ 12:00 am
who wrote this? nd this really helpd out in my project
Aiden
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Jan 24, 2011 @ 7:07 am
I'm doing a research about silicon and this website helped me alot so thank you for making this website... :}}
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Mar 4, 2011 @ 5:17 pm
thanks for the info! it's perfect - no other website i have been on today had better silicon information. :)
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Mar 15, 2011 @ 8:08 am
such a good site helped me so much! how do you reference this in a bibiliography though :/
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Apr 6, 2011 @ 4:04 am
Should have included some of the parameters about silicon
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Apr 13, 2011 @ 9:21 pm
The book OUR STOLEN FUTURE references about silicon, I have not had the opportunity to read it, but one of my Enviromental Ill friends suggests that I should stop producing solar stills which purifies water via sun energy to creat pure water. I use food grade silicone to produce these stills, about 20 tubes in all. Her suggestion is that the toxins emitted from the silicone goes into the water. I have assured her that there is no polycarbonates or other toxins present. Your input would be grateful to clear any misinformation. Thank you in advance.
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May 10, 2011 @ 4:04 am
I really appreciate your efforts which helped me a lot with my project.
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Aug 30, 2011 @ 7:19 pm
WHAT AN EXPLANATION.I NOW PORTRAY MYSELF AS EXPERT IN THIS LEVEL.WELL! I ALREADY FINISH MY ASSIGNMENT BECAUSE OF THIS INFORMATION!KEEP IT UP YO!!!:)(:
yo
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Sep 8, 2011 @ 8:20 pm
Great info. Helped me a lot with health concerns of silicon dioxide.
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Oct 3, 2011 @ 12:12 pm
This was a great resource. Thank you so much for all the information. It was very organized and brief.
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Oct 21, 2011 @ 1:01 am
thank you for all the information , i hope i will use it fo my project
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Oct 30, 2011 @ 10:10 am
thanks for your information..
i was helped with this blog
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Nov 18, 2011 @ 7:19 pm
in this site i already found information. i wish you had topics like texture or odor or flammability.
nadia
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Dec 13, 2011 @ 11:11 am
i relly lyke this website becuse it helpes me with sum of my prodjects at skhool sumetimes
poop face
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Feb 6, 2012 @ 1:13 pm
i hate this website it was not helpfull at all you guys suck hard (thats what she said)
googoo
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Feb 17, 2012 @ 7:07 am
What 3 metals align with silicon because I have a science project and i need to know
Alliase
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Mar 4, 2012 @ 6:18 pm
Amazing Amazing help! You basiclly wrote my paper for me.(; I love and appreciate you all so
much! Thank you thank you thank you!
Hannah taylor
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May 13, 2012 @ 12:00 am
I was wondering how accurate this site is because i have a science assignment and i want the information to be correct ?
Munivel
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Aug 1, 2012 @ 6:06 am
Nice article well explained about the silicon as its very necessary to me understanig about the silicon in the welding of cast iron.thank you sir...
Harry styles
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Sep 8, 2012 @ 8:20 pm
Thanks this website was so helpful. You helped a lot with my project
Emma
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Sep 23, 2012 @ 2:14 pm
Wow, thanks so much! Really helped improve upon my project :D
Dakota
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Oct 9, 2012 @ 3:15 pm
Thanks so much if it wasnt for this website I would have failed but instead I got an A+
Lesly
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Oct 25, 2012 @ 2:14 pm
I was wondering why they named silicon silicon but I still can't find it so can you guys help me please? =D
Autumn
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Nov 27, 2012 @ 7:07 am
Thank you so much for helping me with my science project...this website has helped me alot!
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Dec 8, 2012 @ 4:04 am
SCIENTIST ARE ALWAYS ACHIEVERS I RELISH THIS RESEARCH ONE DAY I WILL DISCOVER MINE WATCH OUT...
Jake
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Dec 19, 2012 @ 10:10 am
Where was si discovered? thanks to whoever answers this?
gonzalo
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Feb 18, 2013 @ 6:18 pm
what are some physiscal changes? thankes for whoever answers this?
Sergei
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Mar 11, 2013 @ 9:21 pm
Thank you. I got affected by this element.thank you
Emma F.
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Apr 25, 2013 @ 7:19 pm
Thank you. You just helped identify my mysterious compound for my Chem. project!
Pat Anthony
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Oct 6, 2013 @ 11:11 am
What do they mean by space aged silicon? How many compounds are make up to produce the food grade silicon
jb lover
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Nov 5, 2013 @ 7:19 pm
my teacher gave us this dumb assignment and this really helped THANK YOU :) :) :)
nicole_ini
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Nov 8, 2013 @ 3:03 am
cheers for the website, helped loads, cheers bud x
od and jblover
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Nov 13, 2013 @ 11:11 am
Thanks for the website it really helped me on my project in school thanks for the website it is really helpful to people. THANKYOU VERY MUCH
Audrey
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Dec 3, 2013 @ 6:18 pm
This is a wonderful site. It really did help me do my research for my class project. : )
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Mar 22, 2014 @ 5:05 am
hi
I want refractive index of silicon for PCW modeling
please
Chemistry Student
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Oct 2, 2014 @ 7:07 am
Very helpful for my project, well organized, may want to get some color images though.
Grade 9 Student - BDHS
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Oct 8, 2014 @ 5:17 pm
Thanks so much, helped so much for my project --- Had to create a story based on the element, telling our science teacher when we were 'found' and stuff like that.

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