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Metallic silicon


A naturally occurring nonmetallic element. Silicon was discovered in 1787 by Lavoisier but not isolated until 1824 by Baron J. J. Berzelius, a Swedish chemist. It is the second most abundant element in the earth's crust (at 27.6%), but silicon does not occur free in nature. It is a major portion of Silica (Sand, Quartz, Flint, Onyx, etc.) and silicates (Granite, Clay, Mica, Talc, etc). Pure silicon is a hard, dark gray solid. It oxidizes in hot air to form a protective oxide layer. Silicon is used in the manufacture of electrical components (transistors, diodes, semiconductors, etc.), alloys (Silicon bronze, Silicon brass, Steel, etc.) and abrasives (Silicon carbide). Silicon also forms stable Silane, Siloxane, and Silicone compounds.

Synonyms and Related Terms

Si; silicium (Ned., Fr., Deut.) ; silicio (It, Esp.); silício (Port.); Kisel (Sven.)


  • Powder is flammable.
  • Sensitive to moisture.
  • Contact may cause irritation.
  • Fisher Scientific: MSDS

Physical and Chemical Properties

Soluble in alkalis and a mixture of nitric and hydrofluoric acids. Insoluble in water, nitric acid, hydrochloric acid.

Composition Si (atomic no. 14)
CAS 7440-21-3
Mohs Hardness 7.0
Melting Point 1410 C
Density 2.33 g/ml
Molecular Weight atomic wt = 28.0855
Boiling Point 2355 C

Resources and Citations

  • G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 710
  • Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
  • Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
  • Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
  • The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983 Comment: entry 8635
  • The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998 Comment: gives discovery date as 1823 by Baron Berzelius