Periodic Table

Radon

Noble Gas

Quick Facts about Radon

At
  • gas- state of matter at room temperature
  • Radioactive- no stable isotopes exist
  • 0- common oxidation states in compounds
  • FCC- crystal structure, atomic arrangement in solid form
Fr

Radon (Rn) is element 86 on the periodic table. Atomic mass of Rn: 222.0000 u. Rn is in period 6, group 18. Melting point of Rn: 202.00 K.Density of Rn: 0.01 g/cm³.

Why Radon Matters

The invisible radioactive gas seeping into homes worldwide

In Your Home

  • May be present in basement air (from soil)
  • Radon detectors in some homes
  • Can dissolve in well water
  • Accumulates in poorly ventilated spaces

Industry Uses

HealthHome radon testing kits and mitigation systems
ResearchEarthquake prediction research (radon release patterns)
MedicineHistorical use in cancer treatment (radon seeds)
MiningIndicator of uranium deposits

In Your Body

✗ Not essential

No biological function. Radioactive decay products can damage lung tissue. Second leading cause of lung cancer after smoking.

Safety: Highly dangerous due to radioactivity. Alpha particles from decay damage lung cells. EPA recommends action at 4 pCi/L.

Discovery of Radon

Discovered by Fredrich Ernst Dorn in Germany, 1898

Name origin: Variation of the name of another element, radium.

History & Events

1900
Discovery
Friedrich Ernst Dorn discovered radon as a radioactive gas emitted by radium
1984
Watras Incident
Stanley Watras set off radiation alarms at a nuclear plant—traced to radon in his home (100x safe limit)
1988
EPA Action
US EPA recommended nationwide radon testing after realizing widespread home contamination

About Radon

Colorless radioactive gaseous element, belongs to the noble gases. Of the twenty known isotopes, the most stable is Rn-222 with a half-life of 3.8 days. Formed by the radioactive decay of Radium-226. Radon itself decays into Polonium. Used in radiotherapy. As a noble gas, it is effectively inert, though radon fluoride has been synthesized. First isolated in 1908 by Ramsey and Gray.

Atomic Properties of Rn

Atomic Number of Rn
86
Atomic Mass of Rn
222.0000 u
Electron Configuration
[Xe] 4f14 5d10 6s2 6p6
Electronegativity
2.20
Block
p-block
Group
18
Period
6

Physical Properties of Rn

Phase (STP)
gas
Melting Point of Rn
202.00 K
Boiling Point of Rn
211.50 K
Density of Rn
0.0097 g/cm3

Thermal Properties

Heat of Vaporization
18.10 kJ/mol
Specific Heat
0.09 J/g·K
Molar Heat Capacity
20.79 J/mol·K
Thermal Conductivity
0.00 W/m·K

Atomic Radii

Covalent
142 pm
Van der Waals
220 pm

Common Misconceptions

Wrong:Radon only affects old houses.
Correct:Radon can accumulate in any building regardless of age. New, well-sealed homes may trap more radon.
Wrong:If my neighbor's house is safe, mine is too.
Correct:Radon levels vary dramatically even between adjacent houses due to soil composition and construction.
Wrong:Radon testing is expensive and complicated.
Correct:DIY radon test kits cost $15-30 and are simple to use. Professional tests are also affordable.

Isotopes of Radon

Radon has 0 naturally occurring isotopes, plus 3 notable radioactive isotopes.

IsotopeAtomic Mass (u)AbundanceHalf-LifeDecay Mode
21186Rn (Rn-211)Radon-211 isotope210.990601114.6 hoursα, EC
22086Rn (Rn-220)Radon-220 isotope220.011394155.6 secondsα
22286Rn (Rn-222)Radon-222 isotope222.01757823.82 daysα

Data source: NIH PubChem (aggregated from IUPAC, NIST)

Isotope Applications

Isotopes of Radon have important real-world applications in science and industry.

Geochronology & Dating

222Rn has been used as a tool to date groundwater in combination with other isotopes or elemental ratios (i.e. helium/radon and xenon/radon amount ratios) [568], [574].

Abundance

Earth's Crust
4.00×10-13 mg/kg
Seawater
6.00×10-16 mg/L

Uses

Used to treat some forms of cancer.

Sources

Formed from the decay of radium in Earth's crust. Seeps through soil into buildings.

Geochemistry

Goldschmidt
synthetic
Geochemical Class
U/Th decay series

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