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Francium

physical science Maturity 9-11 Next article →

Francium is a very rare and unusual chemical element. It has the symbol Fr and the atomic number 87. This element is an alkali metal, which is a group of metals that react easily with other things.

Pichblende
Pichblende

It is actually the second rarest element found in nature. Only astatine is rarer than francium. Because it is so unstable, scientists have never seen a large piece of it. If you could gather enough francium together, it would likely look like a highly reactive metal. However, the heat from its decay is so strong that it would turn into a gas immediately.

franciumtrap
franciumtrap

How does francium work if it is so unstable? The secret lies in its radioactivity. Most francium atoms break apart very quickly. The most stable version is called francium-223. This version has a half-life of only 22 minutes. A half-life is the time it takes for half of a sample to decay. When francium-223 decays, it turns into other things like radium, radon, or astatine.

franciumtrap
franciumtrap

This constant breaking apart is why the element is so hard to study in large amounts. Scientists have only ever made a tiny cluster of about 300,000 atoms in a lab.

Finding francium was a big moment in science history. It was discovered by a scientist named Marguerite Perey. She found it in France on January 7, 1939. Before she found it, scientists called it eka-caesium. They used this name because they guessed it would be below caesium on the periodic table. It was the very last element to be discovered in nature. Most other elements were made by scientists in labs, but francium was found in the world.

Pichblende
Pichblende

There are many interesting facts about where francium lives. You can find tiny traces of it in uranium ores. In these ores, francium-223 is constantly forming and then decaying. There are 37 known isotopes, or versions, of francium. These versions have different atomic masses ranging from 197 to 233. Most of these versions are synthetic, which means they are made by people in labs. Only two versions, francium-223 and francium-221, occur naturally.

Pichblende
Pichblende

Even though it is too rare to use in stores, francium is still useful. Scientists use it to study the tiny parts of an atom. They use a special tool called a magneto-optical trap to catch it.

franciumtrap
franciumtrap

This helps them learn about energy levels and how subatomic particles work together. Some people even thought it might help doctors find cancer, but that was too hard to do. Today, it remains a wonderful tool for learning about the deep secrets of chemistry.

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