Chemical element · reference page

86Rn

Radon

Radon is element 86 (Rn), located in period 6, group 18 and the p block. At room temperature its reference phase is gas. Its electron configuration is [Xe] 4f14 5d10 6s2 6p6.

Atomic number86

Standard atomic weightNo standard atomic weight

Group18

Period6

Blockp

Electron configuration[Xe] 4f14 5d10 6s2 6p6

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

Radon is monatomic under ordinary conditions. Noble-gas compounds are unusual, but the heavier members can form compounds under strongly oxidising conditions; xenon chemistry in particular includes well-characterised fluorides and oxides.

Physical behaviour

State and phase changes

The reference phase at room temperature is gas. The listed density is 9.73 g/L. The melting point is 202 K (-71.15 °C). The boiling point is 211.5 K (-61.65 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where radon is found and used

In practice, radon is encountered in geology, health and scientific research.

In practice

Examples of real uses

Geology

Isotopes, minerals or decay products are used to trace geological processes and the history of rocks.

Health

Radon is important mainly because exposure, radioactivity or biological effects must be measured and controlled.

Scientific research

Radon is produced, isolated or measured mainly to test atomic, nuclear and periodic trends rather than for bulk commercial use.

Periodic position

What its neighbours tell us

Radon is in period 6 and group 18. In the neighbourhood shown here, astatine is immediately to its left in the same period; xenon is above it and oganesson 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 · 18 · 32 · 18 · 8

Density9.73 g/L

Melting point202 K (-71.15 °C)

Boiling point211.5 K (-61.65 °C)

Pauling electronegativity—

First ionisation energy1 037 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 radon is associated with Friedrich Ernst Dorn. 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

Radon has no standard atomic weight. There is no characteristic terrestrial isotopic mixture from which a stable abundance-weighted average can be assigned.

Radon has no stable isotope. Its isotopes are radioactive, and their half-lives and decay modes become important whenever the element is measured, handled or used.

Safety

Handling and exposure

Radon is radioactive. Work with it requires radiological controls appropriate to the isotope, activity, radiation type and chemical form.