List of 5 Most Radioactive Elements Found on Earth

Naturally occurring radioactive elements are substances whose atomic nuclei are unstable. To become stable, these nuclei spontaneously break down, or decay, by releasing energy in the form of radiation. This process of decay causes the element to transform into a different element over time. The radiation emitted can take several forms, such as alpha particles, beta particles, and gamma rays. The speed at which an element decays is measured by its half-life, which is the time needed for half of the substance to decay.

While all elements can have radioactive forms (isotopes), a few heavy elements, like uranium and thorium, are naturally abundant and are the primary sources of radioactivity found within the Earth's crust. In this article, we'll take a look at the most radioactive elements on Earth, exploring their properties, origins, and significance.

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List of Most Radioactive Elements in the World

Every element is defined by the number of protons in its atoms. However, the number of neutrons can sometimes vary. Atoms of the same element that have different numbers of neutrons are called isotopes. These unstable isotopes decay over time. The time it takes for exactly half of the radioactive atoms in a sample to decay is called the half-life. 

This is a consistent rate and can range from mere seconds to billions of years. A shorter half-life means the element decays and emits radiation much more quickly. Here's the list of the most radioactive elements found on Earth:

1. Polonium

Polonium is one of the most radioactive elements that occurs in nature. It was discovered by Marie Curie in 1898. This element is hazardous because it gives off intense alpha radiation. Even a tiny amount can be deadly. Polonium is found in uranium ores but only in very small amounts. Its most stable isotope, Po-209, has a short half-life of 102 years. It does not have any stable isotopes. Handling polonium requires great care due to its high radioactivity. It is often used as a heat source in space equipment, but only in sealed containers for safety.

2. Astatine

Astatine is a very rare element on Earth. It is also highly radioactive and belongs to the halogen group in the periodic table. Its most stable isotope, At-210, has a half-life of only 8.1 hours. This means it decays very quickly and is hard to study in large amounts. Astatine occurs naturally but only in trace amounts. It is produced when uranium and thorium decay. Because of its short half-life and scarcity, astatine has few uses and is primarily used in scientific research.

3. Radon

Radon is a radioactive noble gas. It is formed naturally from the decay of uranium, thorium, or radium. Its most stable isotope is Rn-222, with a half-life of 3.82 days. Radon gas can accumulate in buildings, especially basements, and is dangerous if inhaled. Radon exposure can lead to lung cancer. Although naturally present in Earth's crust, radon is colourless and odourless, making it hard to detect without special equipment.

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4. Francium

Francium is one of the rarest elements found on Earth. It is highly radioactive, and its most stable isotope, Fr-223, has a half-life of only 22 minutes. Because it decays so quickly, only tiny traces of francium are present at any given time. Francium is produced naturally by the decay of actinium. Its high instability means that it is mainly used for research. No one has ever seen a visible chunk of francium, and it plays almost no role in practical applications outside scientific study.

5. Radium

Radium became famous in the early 1900s after Marie Curie discovered it. It is a highly radioactive metal that emits a faint blue glow. The most stable isotope, Ra-226, has a half-life of 1600 years. Radium decays to produce radon gas. It was once used in glow-in-the-dark paints and medical treatments, but was stopped due to safety concerns. Radium is dangerous because it can cause radiation burns and increase cancer risk.

What Are The Most Radioactive Elements?

The most radioactive naturally occurring element is generally considered to be Polonium (Po), specifically its isotope Polonium-210. It releases a high amount of intense alpha radiation with a relatively short half-life of 138 days, making it extremely dangerous. The heaviest and most radioactive synthetic element known is Oganesson (Og), but it is not found in nature.

Are There 37 Radioactive Elements?

There isn't a single, fixed number because scientists often count differently. There are 28 naturally occurring elements on Earth that have at least one radioactive isotope (known as primordial radionuclides). However, if you include all the synthetic (man-made) elements, which are all radioactive, the total number of elements with radioactive forms is much higher, exceeding 40.

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What Is The Most Toxic Element?

The most toxic element is often considered to be Plutonium (Pu) or Polonium (Po). Plutonium is harmful due to both its chemical effects and its high radioactivity, which can cause cancer even at low levels. Polonium-210 is lethal in microgram quantities if inhaled or ingested because of the massive tissue damage caused by its alpha radiation.

What Is The Devil's Element On The Periodic Table?

The element with the nickname "the Devil's Element" is Phosphorus (P). It earned this name because it was the thirteenth element to be discovered, a number considered unlucky. Also, its highly reactive white allotrope spontaneously glows in the dark and catches fire when exposed to air, giving it a mysterious, dangerous, and sometimes 'hellish' reputation.

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