Radon (Rn)

Radon is a radioactive chemical element with the atomic number 86 in the periodic table. It’s found in the soil and rocks that constitute Earth’s crust. As a member of the noble gas family of periodic table elements, this monoatomic gas has eight valence electrons that prevent radon from making chemical reactions with other chemical elements.

Being a highly radioactive chemical, medicine considers radon both as a Class A carcinogen substance and an important part of cancer therapies. 

Chemical and Physical Properties of Radon

Symbol of RadonRn
Atomic Number of Radon86
Group of RadonNoble Gas
Crystal Structure of RadonCubic: Face centered
Atomic Weight of Radon-222.0176
Shells of Radon2,8,18,32,18,8
Orbitals of Radon[Xe] 4f14 5d10 6s2 6p6
Valence of Radon0
Electro Negativity of Radon0
Atomic Radius of Radon1.34 Å
Atomic Volume of Radon50.5 cm³/mol
Name Origin of RadonVariation of the name of another element, radium.
DiscoveredByFredrich Ernst Dorn
Pronounced of RadonRAY-don
Oxydation States of Radon0
Density of Radon0.00973 g/cm³
Uses of RadonUsed to treat some forms of cancer.
Description of RadonHighly rare and unstable, radioactive metal.
Physical stateGas at room temperature
Electronegativity according to Pauling2.2
Most characteristic isotope222Rn
The energy of the first ionization1037 kJ.mol-1

With the periodic table symbol Rn, atomic number 86, atomic mass of [222] g.mol-1, and electron configuration [Xe] 4f145d106s26p6, radon is an odorless and tasteless radioactive gas with a cubic crystal structure. 

It reaches its boiling point at −61.7°C, −79.1°F, 211.5 K, while the melting point is achieved at −71°C, −96°F, 202 K. 

This member of the noble gas family of elements in the periodic table is 7.5 times heavier than air. It has an electronegativity of 2.2 according to Pauling, whereas the atomic radius according to van der Waals is unknown. 

When exposed to temperatures below its boiling point, radon transforms into a colorless liquid. On the other hand, at even lower temperatures, this radioactive gas turns into an orange-red solid substance that emits intense radiation and glows with a soft yellow light in the dark.

How Was Radon Discovered?

In 1900, the German physicist Friedrich Ernst Dorn (1848-1916) received the credits for discovering the element 86 of the periodic table. While observing radium, Dorn noticed that a gas given off by element 88 emits radioactivity, which he referred to as ‘radium emanation’. 

Eight years later, the British chemists William Ramsay (1852–1916) and Robert H. Whytlaw-Gray (1877–1958) succeeded in isolating radon gas and suggested the name ‘niton’ for the new element. 

How Did Radon Get Its Name?

Element 86 had several names (radium emanation, niton) before it was named ‘radon’, in 1928, after the element in which it was detected for the first time – radium. 

Where Can You Find Radon?

Radon is a naturally occurring gas that can be found in rock, soil, and water. It is formed by the decay of uranium, radium, and thorium, making element 86 highly radioactive. Radon mitigation occurs when groundwater flows and transfers radon gas from Earth’s crust to the surface. From there, it’s released into the atmosphere where it emits radiation. 

Radon in Everyday Life

Despite being one of the most dangerous and toxic gases, radon also has a few practical uses – mainly due to the alpha radiation it emits:

  • Radiation seed therapy is a type of surgical implant by which radon is inserted in the middle of a tumor. Sealed in minute tubes, radon gas decays into radioactive polonium and alpha particles that emit radioactivity, destroying tumorous cells;
  • Radon spas treatments are also common for patients suffering from arthritis. The affected individuals are exposed to high levels of radon in these medicinal spas to relieve the pain caused by rheumatoid arthritis;
  • Before being classified as a high-risk carcinogen substance, radon salts were used in the manufacturing of pants that glow in the dark;
  • Radon gas is often used in geological research and hydrological investigations for examining the interactions between underground waters, creeks, and rivers. Increased radon concentration signifies an underground water source. 

How Dangerous Is Radon?

According to the United States Environmental Protection Agency (EPA), radon is classified as a Class A carcinogen that increases the risk of lung cancer in humans. The National Cancer Institute (NCI) as well as the US Department of Health and Human Services also support this claim by confirming the plentiful biological and epidemiological evidence on the relationship between radon exposure and human lung cancer.

Since this radioactive gas is imperceptible due to the lack of odor or taste, it brings even greater danger to people by being able to enter the living premises without being noticed. Exposure can also occur via radon-contaminated drinking water. 

Exposure to radon does not trigger any side effects, like headache or nausea, for instance. The radioactive particles released during the decay process of radon can be trapped in the lungs and trigger cancer formation. In addition, the increased risk of developing lung cancer is so far the only known health effect after exposure to this radioactive, colorless, and odorless gas. That’s why radon tests are not an uncommon precaution. 

In the United States, radon testing is supported by the following organizations:

  • American Lung Association;
  • National Academy of Science;
  • Environmental Protection Agency (EPA);
  • Centers for Disease Control and Prevention;
  • U.S. Environmental Protection Agency
  • American Medical Association;
  • International Commission on Radiological Protection;
  • U.S. Surgeon General;
  • National Academy of Science;
  • National Council on Radiation Protection and Measurement.

Radon test kits for measuring indoor air quality are available for home use in the United States. If test results show radon levels at or above 4 pCi/L, the USEPA recommends installing a radon mitigation system. 

The CDC also collaborated with the EPA to produce the booklet ‘A Citizen’s Guide to Radon: The Guide to Protecting Yourself and Family from Radon’ that includes all the necessary radon information. You can find more information on the website of the National Radon Program Services

Environmental Effects of Radon

Radioactive radon gas that comes from the soil is a national environmental health problem in the US. Since it easily disperses into the air, the radon-222 isotope is the main radiation source to which we are exposed. In short – radon can be found everywhere!

We breathe in this cancer-causing, radioactive gas every day, but only in extremely low levels so it cannot pose any serious health risks. Moreover, the radioactive radon isotopes decay extremely fast. However, radon still enters homes, schools, and offices through cracks in floors, walls, or foundations. Radon in homes can be released from building materials that contain radon or have been in contact with this toxic substance in nature. 

Regardless of the materials used in the building of a home, any living or enclosed facility can have a radon problem. Since natural radon is released from soil, basements of the houses and buildings typically have the highest level of radon. 

The Consumer’s Guide to Radon Reduction is a radon fact sheet issued by EPA that offers directions on how to regulate radon levels in your home, fix your home, and protect your family from radon exposure. 

Regarding environmental pollution, radon decay products are one of the most hazardous air pollutants. Radon is mostly released by the industries working with this chemical or via human activities. High levels of radon in the water supply can also increase indoor radon air levels. 

In coordination with the World Health Organization (WHO), twenty countries act to repel the deadly radioactive radon gas. The list of countries that partake in this global environmental protection project includes Austria, Brazil, Canada, China, France, Germany, Greece, Ireland, Italy, Luxemburg, Norway, Poland, Russia, Spain, Sweden, Switzerland, Turkey, UK, Ukraine, and the United States. 

Isotopes of Radon

There are 37 isotopes of radium, with atomic mass ranging from 195Rn to 231Rn. All forms of this chemical element are radioactive, which also means that there are no stable isotopes of element 86. Radon-218, radon-220, and radon-22a are the gaseous radioactive products resulting from the decay chain of the radium-226 isotope. 

Main isotopes of radon

Iso­tope Decay
  abun­dance half-life (t1/2) mode pro­duct  
210Rn syn 2.4 h α 206Po  
211Rn syn 14.6 h ε 211At  
α 207Po  
222Rn trace 3.8235 d α 218Po  
224Rn syn 1.8 h β 224Fr  

Source: Wikipedia

List of Radon Compounds

Being classified as a noble gas, radon has a stable outer electron shell. This makes element 86 a rather inert substance that does not readily form chemical compounds. Radon is also the densest substance of noble gasses with a monatomic structure and an oxidation state of zero.

5 Interesting Facts and Explanations

  1. Radon is a serious public health problem in the United States. After tobacco smoke (smoking), radon is the second leading cause of lung cancer in the United States to which an estimated 20,000 lives are lost per year. It’s especially dangerous for non-smokers to whom radon exposure is the first leading cause of lung cancer deaths.
  2. There are two basic types of radon tests: a long-term test (measuring radon levels for a minimum of 90 days) and a short-term test (measuring radon levels for 2-7 days).
  3. According to the US EPA, the recommended action level for indoor radon exposure is 4 picocuries of radon per liter of air (4 pCi/L). Buyers of new homes or real estate are advised to delay or decline a purchase if the seller has not successfully abated radon to 4 pCi/L or less. It’s also advisable to ask about radon-resistant construction techniques used during the construction. 
  4. Radon is one of the first radioactive chemical elements that have been discovered. It had been identified after uranium, thorium, polonium, and radium.
  5. Radon levels in the air tend to be highest during winter, when the air is stagnant and homes are being heated.