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Oxidation & Electrons | Appearance & Characteristics Reactions | Compounds | Radius | Conductivity Abundance & Isotopes 
Silicon crystal structure. |
General:
| Name: Silicon | Symbol: Si |
| Type: Non-Metal, Carbon group | Atomic weight: 28.0855 |
| Density @ 293 K: 2.33 g/cm3 | Atomic volume: 12.1 cm3/mol |
| Discovered: J.J.Berzelius is credited with the discovery of silicon in 1824 when he prepared amorphous silicon. Jacque Deville prepared crystalline silicon in 1854. The element name comes from the Latin word 'silicis', meaning flint. | |
States
| State (s, l, g): solid | |
| Melting point: 1687 K (1414 oC) | Boiling point: 3538 K (3265 oC) |
Energies
| Specific heat capacity: 0.71 J g-1 K-1 | Heat of atomization: 456 kJ mol-1 |
| Heat of fusion: 50.21 kJ mol-1 | Heat of vaporization (sublimation): 359 kJ mol-1 |
| 1st ionization energy: 786.4 kJ mol-1 | 2nd ionization energy: 1577 kJ mol-1 |
| 3rd ionization energy: 3231.4 kJ mol-1 | Electron affinity: 133.6 kJ mol-1 |
Oxidation & Electrons
| Shells: 2,8,4 | Electron configuration: [Ne] 3s2 3p2 |
| Minimum oxidation number: -4 | Maximum oxidation number: 4 |
| Min. common oxidation no.: -4 | Max. common oxidation no.: 4 |
| Electronegativity (Pauling Scale): 1.9 | Polarizability volume: 5.4 Å3 |
Appearance & Characteristics
| Structure: diamond structure | Color: brown (amorphous), gray-black (crystalline) |
| Harmful effects: Silicon is not known to be toxic, but if breathed in as a fine silica/silicate dust it may cause chronic respiratory problems. Silicates such as asbestos are carcinogenic. | Hardness: 7 mohs |
| Characteristics: Silicon is a hard, relatively inert metalloid and in crystalline form is very brittle with a marked metallic luster. Silicon occurs mainly in nature as the oxide and as silicates. The solid form of silicon is unreactive with oxygen, water and most acids. Silicon does react with halogens or dilute alkalis. | |
| Uses: Silicon chips are used in computer circuits. Silica (SiO2) in sand and minerals in clay is used to make concrete and bricks. Silica, as sand, is also a principal ingredient of glass. Silicones are important silicon compunds. Having heat-resistant, nonstick, and rubber-like properties, silicones are often used in cookware, medicine (implants), and as sealants, adhesives, lubricants, and for insulation. | |
Reactions
| Reaction with air: none | Reaction with 6 M HCl: none |
| Reaction with 15 M HNO3: none | Reaction with 6 M NaOH: mild, ⇒ silicates |
Compounds
| Oxide(s): SiO2 | Chloride(s): SiCl4, Si2Cl6 + more |
| Hydride(s): SiH4 (silane), Si2H6 + more |
Radius
| Atomic radius: 110 pm | Ionic radius (1+ ion): pm |
| Ionic radius (2+ ion): pm | Ionic radius (3+ ion): pm |
| Ionic radius (2- ion): pm | Ionic radius (1- ion): pm |
Conductivity
| Thermal conductivity: 149 W m-1 K-1 | Electrical conductivity: 1.2 x 10-5 S cm-1 |
Abundance & Isotopes
| Abundance earth's crust: 27 % by weight, 20 % ppm by moles | |
| Abundance solar system: 900 ppm by weight, 40 ppm by moles | |
| Cost, pure: 5.4 $/100g | |
| Cost, bulk: 0.17 $/100g | |
| Source: Commercial quantities of silicon are obtained by the reaction of silica (SiO 2) and carbon in an electric furnace using carbon electrodes. Very high purity silicon for semiconductors is obtained using the Siemens process - high-purity silicon rods are exposed to trichlorosilane at 1150 oC. | |
| Isotopes: Silicon has 14 isotopes whose half-lives are known, with mass numbers 22 to 36. Of these, three are stable: 28Si, 29Si and 30Si. | |
