Radon: Occurrence, Properties, in Biological System, Uses & Isotopes

Radon is a non-metallic natural radioactive element that belongs to the family of noble gases in group number 18 of the periodic table. The radon’s atomic number is 86 whereas its atomic mass is 222.A single atom of radon contains 86 electrons. It has 86 protons and 136 neutrons in its nucleus. Radon is represented by the symbol “Rn”.
Naming and History

Radon is named after the chemical element radium, because it was discovered from the radium decay chain. It was originally named Niton from Latin, the word used for shine.

Radon is one of the radioactive elements discovered early. In 1899, Robert Owens and Rutherford noticed the release of radioactive gas by thorium. In the same year, Marie Currie and Pierre observed the radioactive gas raised from radium decay.

Friedrich E. Dorn in 1900 at Halle, Germany discovered the radon. He was working with radium when he observed the emanation of radioactive gas during the radium decay chain. In 1900, Rutherford stated an investigation of new gas.

He discovered that it can be condensed into a liquid. In 1908, William Ramsay and Robert Gray collected enough radon to study its properties and announced that it was the heaviest gas known.

Occurrence of Radon

Radon is present in detectable amounts in the atmosphere. Hot water springs, geothermal springs, and geysers contain radon. But today most of the radon is obtained through the radioactive decay chain of radium.

Large samples of radon are collected from decaying radium 226.

Properties of Radon

Radon is odorless, colorless, and tasteless and the densest gas occurs at standard temperature and pressure. Below its freezing point, it shows brilliant phosphorescence. It is radioactive and decays into other elements which are radioactive and toxic.

It is the decay product of radium, uranium, etc. Its most common forms are alpha decay. It is chemically unreactive and has a shorter half-life. It forms a compound Radon fluoride.

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The melting point of radon is -71°C and its boiling point is -61.7°C. It has a density of 0.00973 grams per cubic centimeter. Radon exists as a gas at room temperature.


Radon in Biological System

Radon has no known significant role in living organisms and other biological systems. It is highly radioactive and a carcinogen. It is gas so can be easily inhaled and exposure to living tissues to the radiation can cause severe health hazards. In homes and non-smokers, radon is the major cause of lung cancer.

Uses of Radon
  • It was sometimes used in hospitals to treat cancerous cells and tumors but now safer ways of treatments are available.
  • Radon is widely used in hydrologic research.
  • It is used in geologic research to track mass.
  • Sometimes used in polonium and alpha particles generator in nuclear reactors.
Isotopes of Radon

There are almost 34 isotopes ranging from mass number 195 to 228 are known as radon. It has no stable isotopes but comparatively, the stable isotope is radium- 222 with the half-life of 3.8 days.


  • 1. What is the atomic number of radon?
    • A) 82
    • B) 86
    • C) 222
    • D) 136
    • Answer: B) 86
  • 2. What is the chemical symbol for radon?
    • A) Ra
    • B) Rn
    • C) Rh
    • D) Rd
    • Answer: B) Rn
  • 3. Who discovered radon?
    • A) Marie Currie
    • B) Friedrich E. Dorn
    • C) Robert Owens
    • D) William Ramsay
    • Answer: B) Friedrich E. Dorn
  • 4. Which is the primary source of radon today?
    • A) Hot water springs
    • B) Geothermal springs
    • C) Radium decay chain
    • D) Uranium mines
    • Answer: C) Radium decay chain
  • 5. What is the density of radon at standard temperature and pressure?
    • A) 0.00973 g/cm³
    • B) 11.342 g/cm³
    • C) 1.225 kg/m³
    • D) 0.697 g/cm³
    • Answer: A) 0.00973 g/cm³
  • 6. Which decay mode is most common for radon?
    • A) Beta decay
    • B) Gamma decay
    • C) Alpha decay
    • D) Electron capture
    • Answer: C) Alpha decay
  • 7. What is the freezing point of radon?
    • A) -71°C
    • B) -61.7°C
    • C) -89°C
    • D) -10°C
    • Answer: A) -71°C
  • 8. What is the primary health hazard associated with radon exposure?
    • A) Liver damage
    • B) Lung cancer
    • C) Heart disease
    • D) Kidney failure
    • Answer: B) Lung cancer
  • 9. Which isotope of radon has a half-life of 3.8 days?
    • A) Radon-222
    • B) Radon-226
    • C) Radon-228
    • D) Radon-220
    • Answer: A) Radon-222
  • 10. In which field is radon widely used for tracking mass?
    • A) Meteorology
    • B) Biology
    • C) Geology
    • D) Chemistry
    • Answer: C) Geology
  • 11. What is the historical name for radon?
    • A) Emanation
    • B) Shine
    • C) Niton
    • D) Radium gas
    • Answer: C) Niton
  • 12. What property of radon makes it useful in hydrologic research?
    • A) Radioactivity
    • B) High density
    • C) Chemical reactivity
    • D) Phosphorescence
    • Answer: A) Radioactivity
  • 13. Which isotopes of radon are known?
    • A) 10
    • B) 20
    • C) 34
    • D) 50
    • Answer: C) 34
  • 14. What is the most common form of radon decay?
    • A) Beta decay
    • B) Gamma decay
    • C) Alpha decay
    • D) Electron capture
    • Answer: C) Alpha decay
  • 15. Which gas is sometimes used in place of radon for cancer treatment in hospitals?
    • A) Xenon
    • B) Krypton
    • C) Radon
    • D) Argon
    • Answer: C) Radon
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Introduction: Radon, a natural radioactive element classified under the noble gases, boasts an atomic number of 86 and an atomic mass of 222. Named after radium, it was first discovered in 1900 by Friedrich E. Dorn during radium decay chain research. Initially dubbed Niton, its properties as the heaviest gas were confirmed in 1908 by William Ramsay and Robert Gray.

Occurrence: Occurring detectably in the atmosphere, radon is primarily obtained through the decay chain of radium-226.

Properties: It’s odorless, colorless, and tasteless, exhibiting remarkable properties such as phosphorescence below its freezing point. Despite its radioactivity, radon remains chemically unreactive, often decaying through alpha emission.

Biological Impact: Radon’s significance in biological systems is primarily negative, as its inhalation poses severe health risks, including lung cancer, especially in non-smokers.

Uses: Formerly used in cancer treatment, it’s now employed in hydrological and geological research and occasionally in nuclear reactors.

Isotopes: Radon’s 34 isotopes, including radium-222 with a 3.8-day half-life, contribute to its complex radioactive nature.

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