The Radioactive Element Radon

Core Concepts

In this article you will be able to lear every fact about the Radon element! You will also learn about its risks and how to know if your house is radon free!

Topics Covered in Other Articles

> Noble gases

> Electron configuration and electronegativity

> Xenon , Bismuth, Uranium

>  Isotopes

The element Radon

Introduction to Radon

The Radon element, symbol Rn, is a highly radioactive noble gas, at standard conditions it is colorless and odorless. The radioactive decay of uranium forms this element. Radon decay produces alpha particles and some cancer therapies can use them, however, there are safer therapies nowadays.

Ten facts you should know about Radon

  1. We usually find this element in its gas form in the air and this occurs as the result of uranium breakdown in rocks and soil.
  2.  It was the fifth radioactive element to be discovered.
  3.  It is the second leading cause of lung cancer, but the leading cause among non-smokers.
  4.  This element can become lodged in homes, so there are many test kits to determine the radon levels in your home.
  5.  When the element is cooled below its freezing point (-96 °F or -71 °C), it glows yellow to orange and red if the temperature drops further.
  6.  It is the heaviest gas known, then Xenon is the second.
  7.  The element has 37 known isotopes, all of them are radioactive, and only three of them are natural.
  8.  Friedrich Ernest Dorn discovered the element in 1900 when he was studying radium decay
  9.  Radon’s original name was niton, named after the Latin word “nitens”, shortly in 1923 they changed the name.
  10.  The easiest way to obtain this gas is to isolate it from the air because of its density.

Radon in the Periodic Table

The element radon has the atomic symbol Rn and its atomic number is 86. It is a noble gas, so it’s part of group 18. It is in period 6, it is also located in the p-block of the periodic table with astatine to the left and nothing directly to the right since it is in group 18. Francium is the next atomic number.

It has an electron configuration of [Xe]4f145d106s26p6 or simply [Rn] and an electronegativity of 2.2 on the Pauling scale. As a noble gas, this element has a full octet, consequently, it’s very difficult for it to react.

Applications in Today’s World

Uses of Radon

Medical Uses

Before people knew about the health issues radioactive elements caused, they practiced “radiotorium”, a pseudoscientific therapy that consisted in using radioactive elements in a spa, believing it would cure their illness. Years later, they created a cancer therapy that used alpha particles (formed by radon’s decay) to kill cancer cells in humans with their ionization properties. Another medical use was to treat autoimmune diseases with limited exposure in controlled environments.

Scientific Uses

There have been a lot of scientific breakouts thanks to radioactive elements. Meteorologic scientists gather data about uranium concentration and content in soil to track air masses thanks to the variations in radon emanation. Scientists also use radon content in water to study the interactions between groundwater flow and steam.

Where can we find Radon?

Soils and rocks can contain this element, also burning coal and other fossil fuels may release radon. We can also find diluted radon in the air, which is normal below certain levels. This gas can move from soil and rocks to groundwater and water surface. When natural gas has had previous contact with uranium and thorium rocks and soil, it’s very common for it to contain radon.

History of Radon

When and How was the Element Radon Discovered?

In 1899 Ernest Rutherford and R.B. Owens discovered the 220Rn isotope, a rare isotope of the more common 222Rn. German chemist Friedrich Ernest Dorn, a year later, discovered this radioactive element in 1900 and the 222Rn isotope. He made this discovery while studying the radium decay chain. Radium was used for cancer therapies, but it was really expensive so people used radon believing it would have the same properties, and also be more accessible.

In 1984 the danger of radon in houses began to be known. This started in Pennsylvania with Stanley Watras, a worker at a nuclear plant. They set off the radiation detector despite there being no radioactive material in the plant yet. It was concluded that the radiation was coming from his house, not from a fault on the detector. With this, companies started to sell kits to detect the amount of radon in houses.

radon detection kit
Radon Detection Kit

Radon’s chemistry – Compounds, Reactions and Oxidation States

Isolation of the element

There are two main ways to isolate radon. The first option is to isolate it through the radioactive decay of a radium isotope.

226Ra → 222Rn + 4He

It can also be obtained through the byproduct of the separation of air due to the difference between their densities.


Despite being a noble gas, radon can react with fluoride. This reaction forms radon difluoride (RnF2) or trifluoride (RnF3) which are solid compounds.
These compounds are not very stable and tend to decompose in an attempt to vaporize.

Radon does not react with water but it is slightly soluble, 230 cm3/kg at 20 °C.

Oxidation states

This element has no oxidation states since it is a noble gas

Radon’s decay

The radioactive decay of uranium forms radium, and the radioactive decay of radium forms radon. Radon can also go under radioactive decay, forming other isotopes such as polonium, bismuth, and lead. The most common radon’s decay reaction is when the 222Rn isotope decays into 218Po.

222Rn → 218Po + 4He

When polonium, bismuth, and lead decay, they emit alpha particles that can reach very sensitive cells. These particles can cause cancer due to their poor penetrating power, meaning they leave their energy on every biological cell they pass through.

Physical Properties of Radon

  • Symbol: Rn
  • Melting point: -71 °C
  • Boiling point: -61.7 °C
  • Density (g/L): 9.73
  • Atomic mass: 222
  • Atomic number: 86
  • Electronegativity on Pauling scale: 2.2
  • Classification: Nobel gas
  • Crustal abundance (ppm): 0.0000000000004
  • Electron configuration: [Xe] 4f14 5d10 6s2 6p6
  • Key isotopes: 211Rn, 220Rn, 222Rn
  • Found naturally in minerals: granites and some metamorphic and sedimentary rocks
  • Toxicity: Highly radioactive and therefore toxic

Where can I buy Radon?

You can buy 25mm in length and 5mm in diameter ampules online for $50

Enjoyed reading about manganese? Check out other elements on our INTERACTIVE PERIODIC TABLE!