The periodic table/Silicon

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Silicon is a chemical element which has specific properties useful in modern electronics, such as semi-conduction.

Elemental silicon has two basic forms; amorphous, which has no regular structure, and crystalline, in which the atoms are arranged into a regular lattice. Both forms find use in modern electronics, but crystalline is the most useful form. The growth of silicon crystals is a long and complex process.

Discovery

Silicon was discovered by Jöns Jacob Berzelius in Stockholm in 1824. The name is derived from the Latin 'silex' or 'silicis' meaning flint.

Quick Facts

Name: Silicon

Symbol: Si

Mass: 28.0855

Atomic Number: 14

Electron Configuration: [Ne] 3s² 3p²

Classification: metalloid

CAS Number: 7440-21-3

Appearance: blue-grey powder

Discovery in: 1824

Key Isotopes: ²⁸Si, ³⁰Si

Allotropes: amorphous Si, crystalline Si

Density: 2.329 g/L

Crystal Structure: cubic

Melting Point: 1414 °C

Boiling Point: 3265 °C

Uses

Silicon is one of the most useful elements to mankind. It is used extensively in solid-state devices in the computer and microelectronics industries. For this, hyperpure silicon is needed, prepared by thermal decomposition of ultra-pure trichlorosilane, followed by recrystallization. The silicon is then selectively doped with tiny controlled amounts of boron, gallium, phosphorus or arsenic. Every year, 80,000 tonnes of semiconductor-grade silicon and 8 million tonnes of ferro-silicon are produced for the steel and metallurgical industries. Granite and most other rocks are complex silicates which we use for civil engineering projects. Sand (silicon dioxide or silica) and clay (aluminum silicate) are used to make concrete and cement. Sand is also the principal ingredient of glass, which has thousands of uses. Silicon carbides are important abrasives and also used in lasers. Silicon, as silicate, is present in pottery, enamels, and in high-temperature ceramics.

Silicon is essential to plant life but its use in animal cells is uncertain. Phytoliths are tiny particles of silica that form within some plants. Since they do not rot they provide us with useful evolutionary fossil evidence. Silicon is non-toxic but some silicates, such as asbestos, are carcinogenic. Some workers such as miners and stonecutters who are exposed to siliceous dust often develop a serious lung disease called silicosis.

Atomic Data

Atomic radius: 2.100 Å

Covalent radius: 1.14 Å

Electronegativity: 1.900

Electron affinity: 134.115 kJ mol^-1

Ionisation energies

First: 786.518 kJ mol^-1

Second: 1577.133 kJ mol^-1

Third: 3231.583 kJ mol^-1

Fourth: 4355.519 kJ mol^-1

Fifth: 16090.557 kJ mol^-1

Sixth: 19805.529 kJ mol^-1

Seventh: 23783.616 kJ mol^-1

Eighth: 29287.135 kJ mol^-1

Supply Risk

Unknown

Oxidation States and Isotopes

Common oxidation states: 4, -4

Isotopes

Isotope	Atomic mass	Abundance (%)
²⁸Si	27.977	92.223
²⁹Si	28.976	4.685
³⁰Si	29.974	3.092

Pressure and Temperature Data

Molar heat capacity: 19.99 J mol^-1 K^-1