Silicon (Si)

Silicon is the second most abundant element in the crust at about 28% by mass, and essentially all of it is bonded to oxygen — sand, quartz, granite, clay and glass are all silicon-oxygen frameworks. The wafers used for chips are grown as single crystals up to 300 mm across and are among the purest bulk materials ever made, at better than one impurity atom in a billion. Silicon is a poor conductor and a poor insulator, and that awkward middle position, plus an oxide that happens to be an excellent insulator, is the entire reason the semiconductor industry is built on it rather than on germanium.

Properties

Atomic number

14

Symbol

Si

Standard atomic weight

28.085 u

Category

Metalloid

Group

14

Period

3

Block

p-block

Electron configuration

[Ne] 3s² 3p²

Electrons per shell

2, 8, 4

Melting point

1,687 K — 1413.8 °C — 2576.9 °F

Boiling point

3,538 K — 3264.8 °C — 5908.7 °F

Density

2.3296 g/cm³

Electronegativity

1.9 (Pauling)

Oxidation states

+4, +2, -4

Discovered

1824 by Jöns Jacob Berzelius

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p²

Noble gas shorthand

[Ne] 3s² 3p²

Shells

K: 2 · L: 8 · M: 4

What it is used for

• Integrated circuits and solar cells
• Silicone rubber, sealants and lubricants
• Glass, which is mostly silicon dioxide
• Ferrosilicon as a deoxidiser in steelmaking
• Silicon carbide abrasives and power semiconductors

IUPAC publishes an interval, [28.084, 28.086]; 28.085 is the conventional value. Silicon and silicone are different things: the element, and a family of synthetic polymers built on silicon-oxygen chains.

Neighbours in the table

Group 14

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Silicon sits in group 14 with carbon, germanium, tin, lead, flerovium.