Silicon

14
Si
Group
14
Period
3
Block
p
Protons
Electrons
Neutrons
14
14
14
General Properties
Atomic Number
14
Atomic Weight
28.0855
Mass Number
28
Category
Metalloids
Colour
Gray
Radioactive
No
From the Latin word silex, silicis, flint
Crystal Structure
Tetrahedral Packing
History
In 1800, Sir Humphry Davy thought silica to be a compound and not an element; but in 1811, Gay Lussac and Louis Jacques Thénard probably prepared impure amorphous silicon by heating potassium with silicon tetrafluoride.

In 1824 Jöns Jakob Berzelius prepared amorphous silicon by the same general method.

Henri Deville in 1854 first prepared crystalline silicon, the second allotropic form of the element.
Electrons per shell
2, 8, 4
Electron Configuration
[Ne] 3s2 3p2
Si
Silicon also has the unusual property that it expands as it freezes
Physical Properties
Phase
Solid
Density
2.3296 g/cm3
Melting Point
1687.15 K | 1414 °C | 2577.2 °F
Boiling Point
3538.15 K | 3265 °C | 5909 °F
Heat of Fusion
50.2 kJ/mol
Heat of Vaporization
359 kJ/mol
Specific Heat Capacity
0.705 J/g·K
Abundance in Earth's crust
27%
Abundance in Universe
0.07%
Close
Image Credits: Wikimedia Commons (Enricoros)
Close up photo of a piece of purified silicon
CAS Number
7440-21-3
PubChem CID Number
5461123
Atomic Properties
Atomic Radius
111 pm
Covalent Radius
111 pm
Electronegativity
1.9 (Pauling scale)
Ionization Potential
8.1517 eV
Atomic Volume
12.1 cm3/mol
Thermal Conductivity
1.48 W/cm·K
Oxidation States
-4, -3, -2, -1, 1, 2, 3, 4
Applications
In the form of sand and clay it is used to make concrete and brick; it is a useful refractory material for high-temperature work, and in the form of silicates it is used in making enamels, pottery, etc.

Silica, as sand, is a principal ingredient of glass.

Silicon chips are the basis of modern electronic and computing.

Silicon carbide, more commonly called carborundum is used in abrasives.
If breathed in as a fine silica/silicate dust, it may cause chronic respiratory problems
Isotopes
Stable Isotopes
28Si, 29Si, 30Si
Unstable Isotopes
22Si, 23Si, 24Si, 25Si, 26Si, 27Si, 31Si, 32Si, 33Si, 34Si, 35Si, 36Si, 37Si, 38Si, 39Si, 40Si, 41Si, 42Si, 43Si, 44Si