Element identity
Atomic number, periodic identity and reference mass/isotope conventions are established and source-reviewed.
Atomic / electronic model
Atomic configurations and orbital teaching models are reference interpretations; heavy-element electronic structure is more complex than a classical shell picture.
Nuclear / isotope data
Half-lives, isotope identities and decay information are taken from evaluated nuclear-data/reference sources and remain isotope-specific.
Material / phase data
Ordinary bulk and phase values are shown only where defensible; solid-state transitions are kept separate from melting.
Geography / safety boundary
Occurrence, discovery and public research context may be mapped. Operational radioactive-material inventories, access routes and sensitive facility details are intentionally not mapped.
The lens describes evidence status, not confidence theatre. “Unknown” is kept unknown, and teaching schematics are not presented as direct measurements.
Radon (Rn)
Radon is element 86, a radioactive noble gas produced naturally in uranium-series decay. Because it can migrate from soil and rock into buildings, its most important real-world lesson connects nuclear decay, gas transport and indoor exposure without turning the page into a site-specific risk assessment.
Radon atomic number, mass, electron configuration and key properties
Radon: quick answers
How many protons, neutrons and electrons does radon have?
Radon’s atomic number is 86, so every radon atom has 86 protons, and a neutral atom also has 86 electrons. Radon has no stable isotopes, so the number of neutrons depends on which isotope you mean.
What is the symbol for radon?
The chemical symbol for radon is Rn.
Is radon a solid, liquid or gas at room temperature?
Radon is a gas at room temperature (about 25 °C).
What family (group) is radon in?
Radon is a noble gas, in group 18, period 6 of the periodic table.
How many valence electrons does radon have?
Radon has 8 valence electrons, the electrons in its outer shell, which matches its position in group 18.
What is the electron configuration of radon?
The ground-state electron configuration of radon is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶.
From atomic number to chemistry
Read these as a chain of causes, not as isolated facts. Each step links to the concept hub if you want the underlying idea explained.
Eighty-six protons define radon.
A closed shell explains noble-gas chemistry.
Radon is the radioactive noble gas below xenon.
Rn-222 is central to indoor-radon science.
Radioactivity is nuclear and independent of noble-gas electron-shell closure.
Radon in its period and family
Radon is in Group 18, Period 6 below xenon. Its closed electron shell explains noble-gas chemistry, while radioactive instability comes from the nucleus and is not predicted by valence electrons.
Radon Visual Lab
Decode radon’s tile, rotate a ²²²Rn teaching nucleus and monatomic gas model, inspect occupied 6s/6p probability models, and connect uranium/radium decay to indoor radon, half-life, geology and evidence-based public-health context.
Every mark points to one exact feature
The numbered markers explain the same information system used throughout Element Lookup. Unknown or predicted fields remain visibly labelled rather than being replaced with guesses.
Radon in one minute
Atomic number 86 means every radon nucleus contains 86 protons.
Neutral radon has a closed-shell [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶ configuration.
Radon is a noble gas chemically but has no stable isotopes.
²²²Rn has a half-life of about 3.8 days and arises in the uranium-238 decay series through radium-226.
Radon exposure risk depends on concentration and time; building-specific levels require measurement rather than a generic map.
Shell rings organize electron counts. They are not electron trajectories or orbital shapes.
2 · 8 · 18 · 32 · 18 · 8 electrons
The 6s and 6p models are isolated-atom probability distributions. They explain electronic shell closure, not radioactive decay; alpha decay is a nuclear process.
At ordinary conditions radon is a monatomic gas. The material viewer therefore shows separated atoms, not a molecule or room-temperature lattice.. The viewer is evidence-aware: measured structures are identified as such; unknown bulk structures stay unknown.
Teaching visualization; not a literal finite sample or thermal trajectory.What this model does—and does not—show
The 6s and 6p models are isolated-atom probability distributions. They explain electronic shell closure, not radioactive decay; alpha decay is a nuclear process.
Where do I meet radon?
Clickable learning cards connect the element to materials, environment, technology, biology or research - depending on what the evidence actually supports.
Indoor radon
Radon can enter buildings from soil and rock. Indoor concentration depends on local geology, building pathways, ventilation and other conditions.
Closed-shell noble gas, unstable nucleus
Radon is a clean demonstration that chemical stability and nuclear stability are different questions.
Noble-gas shell
Rn has a closed 6p6 outer shell, so its ordinary chemistry is noble-gas-like.
Xenon, radon and oganesson: closed shells do not guarantee nuclear stability
Group 18 organizes electron-shell closure while nuclear stability changes independently.
| Outer shell | 5s² 5p⁶ |
|---|---|
| Stable isotopes | several |
| Outer shell | 6s² 6p⁶ |
|---|---|
| Stable isotopes | none |
| Rn-222 | t½ ≈3.8 d |
| Period | 7 |
|---|---|
| Evidence | superheavy / predicted chemistry |
Radon properties: atomic, physical, thermal and chemical
Categories follow the science of this element rather than a fixed decorative template. Each row carries condition/provenance context and an evidence label; unknown values stay unknown.
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Atomic number | 86 | Source-reviewed; see Sources below | Evaluated |
| Relative atomic mass | [222] | Source-reviewed; see Sources below | Evaluated |
| Ground-state electron configuration | [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶ | Source-reviewed; see Sources below | Evaluated |
| Group / period / block | Group 18 · Period 6 · p-block | Periodic-table placement | Evaluated |
| Electronegativity | Unknown / not routinely assigned | Source-reviewed; see Sources below | Evaluated |
| Reference isotope | ²²²Rn | Source-reviewed; see Sources below | Evaluated |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| State context | Colorless radioactive gas at 20 °C | Source-reviewed; see Sources below | Evaluated |
| Density | 0.009074 g/cm³ · gas reference | Source-reviewed; see Sources below | Evaluated |
| Material / molecular structure | Monatomic radon gas · ordinary-state model | At ordinary conditions radon is a monatomic gas. The material viewer therefore shows separated atoms, not a molecule or room-temperature lattice. | Measured |
| Classification | Radioactive noble gas | Periodic-table / chemistry classification | Evaluated |
| Structure-model scope | At ordinary conditions radon is a monatomic gas. The material viewer therefore shows separated atoms, not a molecule or room-temperature lattice. | Teaching visualization; exact crystallographic coordinates are not implied unless stated. | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Melting / transition reference | 202 K | Source-reviewed; see Sources below | Evaluated |
| Boiling / gas reference | 211.5 K | Source-reviewed; see Sources below | Evaluated |
| Phase-path context | At approximately standard pressure, radon is solid below about 202 K, liquid to about 211.5 K, and gaseous above. The ordinary room-temperature material view is therefore a monatomic gas. | Shared phase registry drives the slider, regions and markers. | Evaluated |
| Condition warning | Temperature and pressure define phase behavior; purity/allotropy may matter. | Teaching condition statement | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Common oxidation states | 0 dominant · limited compound chemistry exists | Source-reviewed; see Sources below | Evaluated |
| Ion / common ion context | No common stable monatomic ion | Source-reviewed; see Sources below | Evaluated |
| Periodic chemistry context | Radon is in Group 18, Period 6 below xenon. Its closed electron shell explains noble-gas chemistry, while radioactive instability comes from the nucleus and is not predicted by valence electrons. | Element-specific interpretation | Reviewed |
| Chemistry caution | Elemental form, ions and compounds are distinct chemical objects. | Interpretive teaching rule | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| ²²²Rn | Radioactive · half-life about 3.8 days | The most important isotope for indoor-radon exposure and the teaching nucleus on this page. | Evaluated |
| ²²⁰Rn | Radioactive · short-lived | Sometimes called thoron; it belongs to the thorium-232 decay series. | Evaluated |
| Radon isotope family | No stable isotopes | Every radon isotope is radioactive; isotope identity determines half-life and decay-chain context. | Evaluated |
| Teaching nucleus | ²²²Rn · 86 protons + 136 neutrons | Reference isotope used in the nucleus model | Reviewed |
| Property | Value | Context / provenance | Evidence |
|---|---|---|---|
| Page evidence note | Atomic identity, decay and ordinary phase references are measured/evaluated. Geography modes intentionally avoid 'risk pins' because indoor radon is building-specific. Public-health statements are high-level and should be paired with local official guidance. | Evidence summary for this guide | Reviewed |
| Structure evidence | At ordinary conditions radon is a monatomic gas. The material viewer therefore shows separated atoms, not a molecule or room-temperature lattice. | Measured structure, labelled schematic, prediction or explicit unknown as applicable. | Reviewed |
| Map evidence rule | Real pins are reviewed examples; conceptual layers are used when pins would mislead. | Geography Explorer 2.0 | Reviewed |
| Source set | 3 primary/reference links listed below | Open the Sources section for the actual references. | Reviewed |
Is Radon a solid, liquid or gas? State at temperature
At approximately standard pressure, radon is solid below about 202 K, liquid to about 211.5 K, and gaseous above. The ordinary room-temperature material view is therefore a monatomic gas.
Where on Earth is Radon found or produced?
Who discovered Radon, and when?
Radioactive 'emanations' from thorium and radium were observed during the rapid early development of radioactivity science.
Friedrich Ernst Dorn reported the radium emanation later understood as radon.
Radon was recognized as a noble gas and as an important occupational and environmental exposure.
Indoor radon testing and mitigation are established public-health measures in many countries.
How radon enters indoor environments: a non-operational science path
Uranium-238 decay in minerals eventually produces radium-226, which can alpha-decay to radon-222.
As a noble gas, radon atoms can move through pore spaces in soil and rock more readily than solid parent nuclides.
Pressure differences and building openings can allow soil gas to enter indoor spaces.
Indoor concentration is measured with appropriate detectors; public-health agencies provide guidance for interpreting results and mitigation decisions.
What is radon used for?
Public-health measurement
Radon is primarily a hazard to measure and manage rather than a material with broad commercial uses.
Earth and groundwater research
Radon can be used as a tracer in specialized geoscience and hydrology studies.
Historical medicine
Radon and radium were once used in medical contexts that predate modern radiation protection; historical use is not a current recommendation.
Nuclear science
Radon isotopes provide examples for teaching radioactive decay chains and noble-gas behavior.
Radon isotopes and natural abundance
²²²Rn
Radioactive · half-life about 3.8 daysThe most important isotope for indoor-radon exposure and the teaching nucleus on this page.
²²⁰Rn
Radioactive · short-livedSometimes called thoron; it belongs to the thorium-232 decay series.
Radon isotope family
No stable isotopesEvery radon isotope is radioactive; isotope identity determines half-life and decay-chain context.
Five-question Radon check
What is radon’s atomic number?
Why is radon chemically a noble gas?
Which isotope is most important for indoor radon?
Can a world map tell the radon level in one house?
What is radon’s ordinary state at room temperature?
Radon questions students commonly ask
Each answer starts with the direct fact, then explains the chemistry, evidence or material context so the result is understandable rather than merely memorized.
What is radon?
Short answer: Radon is radioactive noble-gas element 86, symbol Rn.
Atomic number 86 means every radon nucleus contains 86 protons. In the periodic table, Radon is classified here as a radioactive noble gas in Period 6 and Group 18. Radon is in Group 18, Period 6 below xenon. Its closed electron shell explains noble-gas chemistry, while radioactive instability comes from the nucleus and is not predicted by valence electrons.
Key point: Rn is element 86; its periodic position and electron structure explain the rest of the page.
Where does radon come from?
Short answer: It forms naturally in radioactive decay chains, especially when radium-226 decays in uranium-bearing rocks and soils.
Radon is element 86, a radioactive noble gas produced naturally in uranium-series decay. Because it can migrate from soil and rock into buildings, its most important real-world lesson connects nuclear decay, gas transport and indoor exposure without turning the page into a site-specific risk assessment. Radon is in Group 18, Period 6 below xenon. Its closed electron shell explains noble-gas chemistry, while radioactive instability comes from the nucleus and is not predicted by valence electrons.
Key point: Use the direct answer together with the material, isotope and evidence context shown elsewhere on the page.
Why is radon radioactive even though it is a noble gas?
Short answer: “Noble gas” describes radon’s electron-shell chemistry; “radioactive” describes the stability of its nucleus. Those are different layers of atomic structure.
Radon has a filled outer electron shell and therefore belongs to Group 18, but its nuclei contain proton–neutron combinations that are unstable. Nuclear decay can occur without requiring ordinary chemical reactivity. This is a useful reminder that electron configuration controls most chemistry while nuclear composition controls isotope stability.
Key point: Chemical inertness does not imply nuclear stability.
Where is radon found?
Short answer: It can occur in soil gas, groundwater and indoor air. Local concentrations vary and are not predictable from a simple world map.
Uranium-238 decay in minerals eventually produces radium-226, which can alpha-decay to radon-222. Indoor radon Radon can enter buildings from soil and rock. Indoor concentration depends on local geology, building pathways, ventilation and other conditions.
Key point: Natural occurrence, resources, production and recycling are different geography questions.
How do I know the radon level in a building?
Short answer: Measure it with an appropriate radon test. Element Lookup does not infer building-specific risk from geography.
Radon exposure risk depends on concentration and time; building-specific levels require measurement rather than a generic map. Radon is element 86, a radioactive noble gas produced naturally in uranium-series decay. Because it can migrate from soil and rock into buildings, its most important real-world lesson connects nuclear decay, gas transport and indoor exposure without turning the page into a site-specific risk assessment.
Key point: Use the direct answer together with the material, isotope and evidence context shown elsewhere on the page.
What is radon’s electron configuration?
Short answer: [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶, a closed-shell noble-gas configuration.
The neutral-atom ground-state reference used on this page is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶. This is an isolated-atom reference: bonding and ion formation can change which outer electrons are present or chemically active. The listed common oxidation-state context is 0 dominant · limited compound chemistry exists, which helps connect the atomic configuration to ordinary chemistry without treating electron counting as a single universal rule.
Key point: Electron configuration is a ground-state atomic reference, not a literal picture of every compound.
Why is radon dangerous?
Short answer: Long-term inhalation of elevated radon increases lung-cancer risk, largely because short-lived radioactive decay products can deposit in the respiratory tract and irradiate tissue with alpha particles.
Radon itself is an inert noble-gas atom chemically, but it is radioactive. After radon decays, its short-lived solid progeny can attach to airborne particles and deposit in the lungs when inhaled. Their alpha emissions can damage nearby cells. Risk depends on concentration and duration of exposure; building radon levels are therefore a measurement problem, not something that can be judged by smell or appearance.
Key point: The main health mechanism involves nuclear decay and inhaled progeny, not ordinary noble-gas chemical reactivity.
Scientific sources for Radon
- Royal Society of Chemistry - Radon
- US EPA - Radon
- NIST - Atomic Data for Radon
- U.S. EPA — Health risk of radon
- U.S. EPA — Radon health effects
Questions to ask next about Radon
A good element lesson should lead to the next useful question, not end after a list of facts.
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