Francium is the chemical element with the chemical symbol Fr. This is the alkali metal element which is also listed as the radioactive metal element. This chemical element also has the other names like eka-caesium and actinium K. Francium’s main characteristic is its instability and rarity. Although this element can be considered as the natural element, but the amount of this element is very rare in the earth. Scientist predicted that there is no more than one-ounce francium element in earth crust in one time.
Francium element is the second rarest natural element after astatine. To use this chemical element in certain applications, scientist must produce this element un-naturally. To make francium element, scientists can do bombarding thorium with protons or bombarding radium with neutrons. This article will cover the francium element uses in limited areas and also its discovery and chemical properties.
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Discovery of Francium Element
Before francium element was discovered, Mendeelev, one of the most influencing scientist in chemistry, has predicted that there must be the element like caesium in the periodic table. This element must have the atomic number of 87 which is placed below caesium in group 1 of periodic table.
Because of this prediction, there were many claims, counterclaims and denials from many scientists regarding the discovery of this element. In the era of 1920s and 1930s, there were some claims about the discovery of this radioactive element in minerals and new lines of the X-ray spectra, but these claims were lack in the scientific evidences.
Francium was firstly discovered by French chemist named Marguerite Catherine Perey in 1939. She successfully found this chemical element while doing analysis in decay sequence of actinium element. On that experiment, she was doing purifying process of actinium-227 when she detected the beta emission from the unknown isotope. At that time, she had done purifying the Actium from all known radioactive impurities but she still detected the radioactivity emission from another element. She concluded that this element was the missing 87 element.
This element was firstly known as Actinium K. This chemical element has the similar properties to the eka-caesium. After that, some experiments were conducted to challenge and analyze Perey’s discovery. And after Word War II, this discovery was finally confirmed in 1946. This radioactive element was named Francium by Perey from the name of her country, France.
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1. Francium Element Uses in Chemical Research
Francium is not the popular chemical element which is used extensively in the commercial application. This is due to its instability properties and its limited amount in the nature. We can only see francium element uses in limited applications in certain fields. The main use of this chemical element is for research purposes in the field of chemistry and atomic structure. The popular use of francium in the chemical research is for defining the Actium element in the natural object.
As francium has very short life, this chemical element can be the great choice for Actium element research. Previously, scientist conduct the experiment to determine Actium in nature by making measurement from all 227Ac decay products’ activities. The experiment is done in three months after they reach the equilibrium state. Mme.tutunan Perey then introduced the newer method to determine this Actium element by francium element which is one of Actium’s possible derivative.
To do this research, francium should be separated from Actium in 3 hours after it has been isolated from the natural products. Then the b—activities of 223Fr is measured. This kind of approach gives scientist enough accuracy in the occurrence of other radioactive elements. And more importantly, this new Actium determination method takes significantly less time than the old method. Francium element uses in this method can make this experiment faster without lowering the quality of its experiment result.
2. Francium Element Uses in Biological Research
Besides its use in the chemical related research, francium also has the benefit in the biological research. Francium element has the promising ability for the cancer detection method. The francium element, especially 223Fr, can be used in the early detection for sarcoma. In one research, francium (Fr), together with Rb and Cs are injected to the different organs in rats.
The experiment showed that these alkali metal elements accumulated in the rats’ kidney, liver, bladder, gut and saliva. In certain rats which having cancer, francium concentrated selectively in the tumor. The activity of francium increased in the affected tissue on that rats. From this research, we can see that francium might have the promising use as the new diagnostic method for cancer disease. This francium element also has no harm to the organism as either 223Fr or 212Fr has very short lifetime.
However, it’s still unclear whether this approach can be applied to organism. This kind of francium element uses still need further studies and experiments as francium still has some issues like its instability and very short life period. There must be detailed research to be conducted to see how this chemical element can be useful in the oncology field.
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3. Francium Element Uses in Atomic Structure Research
Another francium element uses in chemical field is in atomic structure research. Francium element is the good choice for the special spectroscopy experiments. Francium becomes the great subject for this field due to its capability to be trapped, cooled and synthesized. Francium element also possess the simple atomic structure, so that it would be easier for scientist to conduct experiment using its simple form.
The spectroscopy experiments using francium element has given the better information about atomic structure like the energy level and coupling constants in the subatomic particles. This experiment is conducted by emitting the light from the laser-trapped francium 210Fr ions. The result from this experiment gives us more accurate data on the transitions in the atomic energy level. This result of francium experiment is pretty much similar to the prediction from quantum theory.
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4. Francium Element Isotopes
Francium has the 34 known isotopes having the mass of 199 to 232. It has seven meta-stable nuclear isomers. The only occurrence of francium isotopes in nature are Francium-223 and Francium-221. The most stable isotope, Francium-223, has the half-life about 21.8 minutes. This isotope decays into radium-223 through beta decay process or decays into astatine-219 through alpha decay process.
You can find Francium naturally in the uranium minerals. The amount of this element is just one francium atom in billion billion atoms of uranium. This few amounts of francium-223 are the result of radioactive decay product from Actium-227. The actium-227 itself is the part of uranium-235 decay product. Since it has very short life time, scientists predict that there’s probably less than 30 g of francium in crust of Earth at any one time. Another method to obtain francium is using synthesis process. Francium is synthesized in the nuclear reaction as follow:
197Au + 18O → 210Fr + 5 n
This synthesis process is introduced by Stony Brook Physics which can build up francium isotopes with mass of 209, 210 and 211. These isotopes then can be isolated by magneto optical trap or MOT. The production amount of francium is very dependent to the energy level of oxygen beam.
Chemical Properties of Francium Element
As mentioned before, Francium has the chemical symbol Fr and atomic number of 87. It has the atomic weight of 223 (from isotope Fr-223). The melting point of francium is approximately 27 degree Celsius while its boiling point is about 680 degree Celcius. Francium is the member of group 1 in element periodic table which is also known as the alkali metal group. Francium is also included in the radioactive metal element.
Francium has the instability properties. The most stable state of this radioactive element is the ion Ft+. Just like other alkali metal elements, francium has no tendency to build up colloids or complexes. The chemical absorption properties of francium unfortunately cannot be identified as its most stable isotope only has very short lifetime.
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Unlike many other artificial chemical elements like Pu, Tc, Pm, Np and others, Francium is not able to be obtained in the sufficient amount because the limited life time of its isotopes. Due to this fact, the experiment of this chemical element only uses the very low amount of Francium for about less than 10-15 gram. It’s very hard for the scientists to conduct an experiment in exploring Francium properties both its chemical and physical characteristic with this kind of condition.
In the periodic table of element, francium is considered as the most electro-positive element in the Group 1 or Alkali metal group element. This element only exists in 1 oxidation state which is +1. The analysis of francium often uses the analogue from its two above elements, caesium and rubidium. As a prediction, scientist mostly use the chemical properties of Caesium (Cs) and Rubidium (Rb). You will see that most of the chemical properties of francium element is similar to caesium which has the position above francium in the periodic table of chemical element.
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