Periodic Table -> Francium


Francium Details

Francium Symbol: Fr

Francium Atomic Number: 87

Francium Atomic Weight: (223)

What is Francium?

Francium has the symbol Fr and is under number 87 in the periodic table. It used to be known as actinium K and eka caesium and has a metallic color. The chemical properties of francium resemble those of caesium. It is the least electronegative of all the elements in the periodic table, meaning that its atoms are very, very unlikely to attract electrons and thus form negative ions. This is due to the distance of its electrons from the nucleus and its atomic number. What is more, francium is the rarest element that occurs in nature but one. The most rarely occurring one is astatine. This element is extremely radioactive and decays into radon, radium, and astatine. It is classed in the group of the alkali metals. Also known as Group 1 metals, the group of these elements also includes lithium, rubidium, potassium, sodium, caesium, and hydrogen. The last one is an untypical member of the group, even though it is considered a member. All of these elements are located in the s-block, meaning that their outermost electron lies in the so-called s-orbital.

Francium was discovered in 1939 in France by Marguerite Perey. It was named after the country, of course. This is the last natural (not synthetic) element that has been found by scientists. The element is very rare. Small parts of it can be found in the ores of thorium and uranium. More specifically, one of its isotopes can be found in these ores. Very little of it can be found in the Earth’s crust – 30 g at the most at any point in time. None of its other isotopes can be found in nature, and it does not have stable isotopes.

Francium itself is very unstable. Its least volatile isotope, francium-223, has a half-life of just twenty two minutes. Through alpha decay, it decays into astatine-219, and through beta decay into radium-223. This element is also the least stable compared to each synthetic element prior to element number 105.

Given that francium is so rare and not enough of it occurs naturally, researchers have to produce the element as to study its properties. Thorium is bombarded with protons to produce francium or alternatively, radium is bombarded with neutrons. Notably, francium has not been isolated in its pure form. Any amount produced is predicted to decompose due to its high radioactivity.

Francium is a very heavy element. In fact, its equivalent weight is the highest compared to those of all other elements. It is not clear what the melting point of this element is because it is extremely rare and radioactive. Some researchers claim that its melting point is around 27 °C. The element is probably liquid because as other radioactive elements, it gives off heat. Therefore, its boiling point is not known either. Being so rare and unstable, this element has practically no applications. It can be used for basic research only. Its application as a diagnostic aid for different types of cancers has been researched, but this was found impractical.

On the positive side, this element has a pretty simple atomic structure and can be easily cooled, trapped, and synthesized. This is why it has often been used in spectroscopy experiments. Data from these experiments shows a number of interesting transitions between atomic energy levels.

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