Chemical element · reference page

10Ne

Neon

Neon is element 10 (Ne), located in period 2, group 18 and the p block. At room temperature its reference phase is gas. Its electron configuration is [He] 2s2 2p6.

Atomic number10

Standard atomic weight20.1797(6)

Group18

Period2

Blockp

Electron configuration[He] 2s2 2p6

Electronic structure

What controls its chemistry

The outer electron shell is filled, which strongly reduces the tendency to gain, lose or share electrons. This is the central reason noble gases are much less reactive than neighbouring groups.

The heavier noble gases are not completely inert: under suitable conditions some form compounds, especially with highly electronegative elements. The group trend is therefore low reactivity, not an absolute prohibition on chemistry.

Chemical forms

Compounds, ions and materials

Neon is monatomic under ordinary conditions. Stable compounds are rare compared with neighbouring groups because the valence shell is filled; the chemistry is dominated by the free atoms and weak intermolecular interactions.

Physical behaviour

State and phase changes

The reference phase at room temperature is gas. The listed density is 0.9002 g/L. The melting point is 24.57 K (-248.6 °C). The boiling point is 27.1 K (-246 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where neon is found and used

In practice, neon is encountered in lighting, lasers and cryogenics.

In practice

Examples of real uses

Lighting

Neon is used because atoms or compounds of this element interact with light in a useful and reproducible way.

Lasers

Neon is used in laser media, optical components or wavelength-specific light generation.

Cryogenics

Neon is used at very low temperatures as a coolant, working fluid or material whose low-temperature behaviour is useful.

Periodic position

What its neighbours tell us

Neon is in period 2 and group 18. In the neighbourhood shown here, fluorine is immediately to its left in the same period; helium is above it and argon 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

Classificationnoble gas

Phase at room temperatureGas

Electron shells2 · 8

Density0.9002 g/L

Melting point24.57 K (-248.6 °C)

Boiling point27.1 K (-246 °C)

Pauling electronegativity—

First ionisation energy2 081 kJ/mol

Electron affinity—

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 neon is associated with Morris Travers. 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 20.1797(6). This value refers to the isotopic composition of natural terrestrial material, not to the mass of one specific atom.

Neon 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 gas is not necessarily chemically toxic, but it can displace oxygen in confined spaces. Ventilation and oxygen monitoring matter in bulk handling.