Chemical element · reference page

14Si

Silicon

Silicon is element 14 (Si), located in period 3, group 14 and the p block. At room temperature its reference phase is solid. Its electron configuration is [Ne] 3s2 3p2.

Atomic number14

Standard atomic weight[28.084, 28.086]

Group14

Period3

Blockp

Electron configuration[Ne] 3s2 3p2

Electronic structure

What controls its chemistry

Group 14 elements have four valence electrons. That makes covalent bonding especially important for the lighter members, while metallic character increases down the group.

For silicon, the electron configuration [Ne] 3s2 3p2 sets the number and energy of the valence electrons that participate in bonding. Structure and oxidation state then determine the properties of its materials and compounds.

Chemical forms

Compounds, ions and materials

Typical compounds include oxides, halides and hydrides. The lighter members can build strong covalent networks or chains, while the heavier elements show increasing metallic bonding and greater importance of the +2 oxidation state.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 2.329 g/cm³. The melting point is 1 688 K (1 415 °C). The boiling point is 3 538 K (3 265 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where silicon is found and used

In practice, silicon is encountered in electronics, solar cells and special glasses.

In practice

Examples of real uses

Electronics

Silicon is used in electronic components or materials where conductivity, semiconducting behaviour, optical response or chemical stability is useful.

Solar cells

Silicon is used in photovoltaic absorbers, contacts, coatings or semiconductor layers that convert light into electrical energy.

Special glasses

Silicon is added to glass to modify refractive index, colour, thermal expansion, radiation response or chemical durability.

Periodic position

What its neighbours tell us

Silicon is in period 3 and group 14. In the neighbourhood shown here, it lies between aluminium and phosphorus in the same period; carbon is above it and germanium below it in the same group. These positions make it possible to compare atomic size, ionisation energy and bonding behaviour with nearby elements.

Reference data

Physical and atomic properties

Classificationmetalloid

Phase at room temperatureSolid

Electron shells2 · 8 · 4

Density2.329 g/cm³

Melting point1 688 K (1 415 °C)

Boiling point3 538 K (3 265 °C)

Pauling electronegativity1.9

First ionisation energy786.5 kJ/mol

Electron affinity134.1 kJ/mol

Values describe the element or neutral atom where applicable. Physical data can depend on allotrope, pressure and measurement conditions.

History

Discovery and identification

The discovery of silicon is associated with Jöns Jacob Berzelius. Recognition of the element, isolation of a pure sample and assignment of its modern atomic number did not necessarily occur at the same time.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is given as the interval [28.084, 28.086]. Natural samples can differ slightly in isotope proportions, so a single universal decimal value would hide real variation between materials.

Silicon has at least one stable isotope. Different isotopes have the same number of protons and therefore the same element identity, but different neutron numbers and atomic masses.

Safety

Handling and exposure

The hazards associated with silicon depend on chemical form, dose and route of exposure. Pure silicon, its ions and its compounds can have very different biological and environmental effects, so safety data should be checked for the actual substance being handled.