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Close up photo of a piece of purified silicon.
Image: Enricoros/Wikipedia (public domain).
Silicon, which has the symbol Si and atomic number 14, is the second most abundant element after oxygen in the earth's crust. Many meteorites are largely comprised of silicon, and silicon is also found in tektites, which were probably formed by the impact of large meteorites on earth's surface. Silicon is also the main component in obsidian rock, a lovely stone created by volcanoes. Because ancient peoples used obsidian as a cutting tool, for weapons, and for ceremonial purposes, it is sometimes found in excavations. As a very young child, I collected a small black obsidian arrowhead at Kettle Falls, Washington, an artifact left behind by the Salish peoples.
Silicon is the "big sister" to carbon, and shares many of the same chemical properties. For this reason, silicon is known as a chemical analogue to carbon. But unlike carbon, silicon a metalloid -- in fact, it's the most common metalloid on earth. "Metalloid" is a term applied to elements that are better conductors of electron flow -- electricity -- than nonmetals, but not as good as metals. This interesting characteristic means that it acts as a semiconductor: silicon atoms can either enhance or block electron movement. This unusual characteristic is shared with another element that we've already met, boron. Silicon semiconductors are found in nearly everything, from computers, digital cameras, and cell phones to refrigerators.
I have not yet written about the periodic table of elements, but I did find this wonderful video that introduces you to the structure of atoms, the concept of valence electrons and chemical bonds, and how these basic principles are harnessed to make functioning silicon solar cells:
You've already met these elements:
Aluminium: Al, atomic number 13
Magnesium: Mg, atomic number 12
Sodium: Na, atomic number 11
Neon: Ne, atomic number 10
Fluorine: F, atomic number 9
Oxygen: O, atomic number 8
Nitrogen: N, atomic number 7
Carbon: C, atomic number 6
Boron: B, atomic number 5
Beryllium: Be, atomic number 4
Lithium: Li, atomic number 3
Helium: He, atomic number 2
Hydrogen: H, atomic number 1
As promised, here's a wonderful interactive Periodic Table of the Elements that is just really really fun to play with!
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