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What Is Radium-226

Radium-226, represented by the chemical symbol Ra-226, is the most common and highly radioactive isotope of radium. It is formed as a by-product of the nuclear reactors that refine thorium and uranium and also occurs naturally in the earth’s crust. It is produced by the decay of uranium-238. Unlike the other radioactive isotopes of radium that decay in just a matter of days, Ra-226 has a half-life of 1600 years [1, 5, 7]. Its mass number is 226 as it has 88 protons (same as the number of electrons in its shells) and 138 neutrons in its nucleus [6]. Its molar mass or molecular weight is 226.025 g/mol and atomic mass is 226.025 atomic mass units (a.m.u) [8, 9].


Alpha Decay of Radium-226 Equation

Ra-226 undergoes decay into radon-222 by losing an alpha particle and simultaneously releasing energy in the form of a gamma ray [3]. The process occurs as some of the atoms are unstable and require releasing of energy to become stable [5].

Alpha Decay of Radium 226 Equation


  1. It finds application in the production of radon [1, 2].
  2. As a component of some industrial devices [1].
  3. In medical research and cancer treatment (brachytherapy, radiation therapy) [1, 5].

Is It Dangerous

The isotope emits alpha, beta and gamma radiation in the form of particles, rays and waves. Hence higher levels of exposure can lead to anemia, cancer, cataracts and teeth fractures [1]. Since it naturally occurs in groundwater, the maximum contaminant levels (MCLs) for Ra-226 and Ra-228 combined in drinking water has been set by the US Environment Protection Agency (EPA) as 5pCi/l [4].

Interesting Facts

  • The Curie, a unit used to measure the activity of a radioactive substance is based on Ra-226 [7].
  • Gamma-ray spectroscopy can detect the isotope [8].

  1. Radium-226 Poisoning –
  2. Chapter 16, first assignment –
  3. Characteristics of Nuclear Reactions –
  4. What is radium? Is it in drinking water? –
  5. Frequently Asked Questions (FAQs) Regarding Radium-226 –
  6. 88 Ra 226 (Z=88, N=138) –
  7. The Element Radium –
  8. Radium RA-226 –
  9. Question: Radium-226 (atomic mass = 226.025402 ) decays to radon-224 –

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