The chemical element francium: structural features and chemical properties. The chemical element francium: characteristics and history of discovery The origin of the chemical element francium

Fractions (eka-cesium) is an element of the main subgroup of the first group of the seventh period of the periodic system of chemical elements of D. I. Mendeleev, with atomic number 87. It is designated by the symbol Fr (Latin Francium). The simple substance francium (CAS number: 7440-73-5) is a radioactive alkali metal with high chemical activity.

History

This element was predicted by D.I.Mendeleev (as Eka-cesium), and was discovered (by its radioactivity) in 1939 by Marguerite Pere, an employee of the Radium Institute in Paris. She also gave him the name in 1964 in honor of her homeland - France.

Receiving

Microscopic amounts of France-223 and France-224 can be chemically isolated from the minerals uranium and thorium. Other isotopes of france are produced artificially using nuclear reactions.
The most common way to obtain france is by nuclear reaction: 197 Au + 18 O → 210 Fr + 5n
Interestingly, gold is used in this reaction. By this reaction, isotopes with mass numbers 209, 210 and 211 can be synthesized. However, all these isotopes decay quickly (the half-lives of 210 Fr and 211 Fr are three minutes, and 209 Fr in 50 seconds).

Physical and chemical properties

Francium is similar in properties to cesium. Always co-crystallizes with its compounds. Since researchers have at their disposal only the smallest samples containing no more than 10 -7 g of francium, information about its properties is known with a rather large error, but they are constantly being updated. According to the latest data, the density of francium at room temperature is 1.87 g / cm³, the melting point is 27 ° C, the boiling point is 677 ° C, and the specific heat of fusion is 9.385 kJ / kg.
Francium has the lowest electronegativity of all currently known elements. Accordingly, francium is the most chemically active alkali metal.

Elements of Mendeleev. By 1925, it was one of four missing elements. It is the heaviest and most active in nature, and it is also the fastest for the half-life of existing chemical elements. This, as well as the low nuclear stability, favored the fact that for a long time it was impossible to discover france, the existence of which was predicted by Mendeleev almost a century before it was obtained.

The history of the discovery of the chemical element France

She is distinguished by the fact that she fell to the fate of a woman whose name is Margarita Pere. The search for this substance was based on On the basis of substances adjacent to No. 87, various hypotheses were put forward about the properties of this metal:

• due to the fact that adjacent cesium melts at room temperature, it was assumed that the 87th element would also melt at low temperatures;
• it was thought to refer to liquid metals such as cesium or mercury;
• hypotheses were put forward about its radioactivity.

By the end of 1938, Margarita Pere joined the search for this substance. She focused her attention on the alpha particles emitted by actinium. She well purified this substance from various impurities, leaving only a pure element. After prolonged chemical treatments, the scientist retained alkaline salts in his hands. She assumed that he was not radioactive, but after evaporation, beta activity became clearly visible with a half-life of 22 minutes. The woman immediately realized that this speed depends directly on the action of the alkaline element.

The long-term work of Margarita was crowned with success only in the fall of 1939. Based on the existing nomenclature, the woman gave the 87th element the name "Actinium-K", which she later renamed in France in memory of the place where she was born. The International Union of Pure and Applied Chemistry adopted the name coined by Margarita Pere. This is how the opening of France took place.

Chemical element Fr: characteristic

It is the heaviest and most active alkali metal found in nature, and it is also one of the fastest chemical elements in existence for half-life. The longest-lived of its isotopes can be found in uranium minerals. Therefore, the chemical element francium is very poorly understood, since it decomposes quickly. Moreover, it has very high radioactivity. But still, small amounts of this element were investigated, and the following properties were found:

It is the last chemical element discovered in nature. It belongs to the rarest, as it is very unstable and quickly decays. According to scientists, the chemical element francium is present on Earth in only 30 grams. It can be attributed to liquid metals, but it is liquid for a short time. After a few seconds, francium breaks down into more stable elements, in particular, radium is obtained.

Application of France

But, despite the high instability, this chemical element also benefits. It is used, although not widely. First of all, the chemical element francium is useful for the detection of actinium in natural objects. In addition, thanks to experiments with laboratory rats, scientists have found that it accumulates in malignant tumors that are in the first stage of development. Therefore, it can be used for early diagnosis of sarcoma. But research on this element continues. Francius reveals more and more of his secrets to scientists.

Francium is an element with an atomic number of 87. The atomic mass of the longest-lived isotope is 223. Francium is a radioactive alkali metal with an extremely pronounced chemical reactivity.

Francium

History of the discovery of france

The metal was discovered back in 1939 by an employee of the Paris Radium Institute named Marguerite Perey. She, apparently, out of patriotic feelings, named the element in honor of her homeland. Francium was discovered while studying the artificially obtained element "actinium": an uncharacteristic radioactive glow was noticed. For the sake of fairness, it should be noted that other researchers could have worked on the creation of this element at the same time, but, as they say, the winners are not judged.

Main characteristics

Today, francium is one of the rarest metals (and indeed chemical elements in general) found in nature.

Earth's crust

According to scientists, the content of this metal in the earth's crust is about 340 grams (only astat is contained less). This is mainly due to his physical instability. Being radioactive, it has a very short half-life (for the most stable isotope it is 22.3 minutes). The only thing that compensates for its natural content is that francium is an intermediate link in the decay of uranium-235 and thorium-232. Thus, all the francium that is found in natural conditions is a product of radioactive decay.

How can you get it?

Let's consider the only way to obtain the most stable isotope of france. This can be done by nuclear reaction of gold with oxygen atoms. All other methods (meaning radioactive decay) are inappropriate, since extremely unstable isotopes are obtained that "live" no more than a few minutes. To get this element at home, like all its compounds, of course, will not work (and there is no need, in fact). many experiments with other metals can be found.

What are the chemical properties of francium?

Francium is similar in properties to cesium. The relativistic effects of the 6p shell ensure that the bond of francium with oxygen in superoxides (for example, of the composition FrO 2) is more covalent relative to superoxides of other elements of this group. Given the lowest electronegativity of all currently existing francium, it is characterized by pronounced chemical activity. All physical properties of this element are indicated only theoretically, since it is not possible to test them in practice due to the short period of "life" of this element (density \u003d 1.87 g / cm³, melting point \u003d 27 ° C, boiling point \u003d 677 ° C, specific heat melting \u003d 9.385 kJ / kg). All compounds of this element are soluble in water (exceptions: salts of perchlorate, chloroplatinate, france picratcobaltinitrite). Francium always co-crystallizes with substances that include cesium. Its coprecipitation with insoluble cesium salts (cesium perchlorate or silicotungstate) is observed. The extraction of france from solutions is carried out:

• chloroplatinates of cesium and rubidium Cs 2 PtCl 6 and Rb 2 PtCl 6;
• chlorobismuthate Cs 2 BiCl 5, chlorostannate Cs 2 SnCl 6 and cesium chloroantimonate Cs 2 SbCl 5 2.5H 2 O;
• free heteropolyacids: silicotungsten and phosphotungsten.

What is the practical significance of this element?

Despite all its uniqueness, francium has not yet been used in practice. Accordingly, it is not used in industry and any technologies. The reason for this is its extremely short half-life. There is evidence that france chloride can be used to diagnose oncological neoplasms, however, in view of the significant cost of this formation, this kind of technique cannot be introduced into systematic use. In principle, cesium has the same properties.

Cesium

So this property of France turned out to be unclaimed: its cost is compared with the cost of a ton of platinum or gold. According to forecasts of leading experts, the element in question will always have a purely cognitive value, nothing more.

0.7 (Pauling scale)

Electrode potential

Fr ← Fr + −2.92 V

Oxidation states Ionization energy
(first electron) Thermodynamic properties of a simple substance Density (at n.a.) The melting temperature Boiling temperature Ud. heat of fusion

~ 2 kJ / mol

Ud. heat of vaporization

~ 65 kJ / mol

Molar heat capacity

31.6 J / (K mol)

The crystal lattice of a simple substance Lattice structure

cubic
body-centered

87
7s 1

Being in nature

Francium is one of the rarest elements. Among the elements that constantly exist in the earth's crust, only astatine has a lower content. All natural francium is radiogenic, its radioactive decay is compensated by the simultaneous appearance of new francium atoms as intermediate decay products of uranium-235 and thorium-232. The total content of france in the earth's crust is estimated at 340 grams.

Isotopes

For 2012, 34 isotopes of france are known with mass numbers 199-232 and 7 metastable nuclear isomers. Nature (as products of radioactive decay of uranium and thorium) contains two isotopes: 223 Fr and 224 Fr. Francium-223 (the longest-lived of the isotopes of france, with a half-life of 22.3 minutes) is one of the side branches of the natural radioactive series of uranium-235 and is contained in extremely small quantities in uranium minerals. Studies of the properties of francium are carried out with indicator amounts of the nuclide 223 Fr (less than 10-15 g), since due to the absence of long-lived isotopes of francium it is impossible to obtain in weight amounts. Formed by alpha decay of actinium-227:

227 Ac → 223 Fr (accompanied by α-radiation, decay probability approximately 1.4%),

The most common way to get france is by nuclear reaction:

$()\; ^\; (197)\; \_\; (79)\; \backslash \backslash \; textrm\; (Au)\; +\; ()\; ^\; (18)\; \_\; (8)\; \backslash \backslash \; textrm\; (O)\; \backslash \backslash \; rightarrow\; ()\; ^\; (210)\; \_\; (87)\; \backslash \backslash \; textrm\; (Fr)\; +\; (\; 5)\; ^\; (1)\; \_\; (0)\; \backslash \backslash \; textrm\; (n)$

Interestingly, gold is used in this reaction. By this reaction, isotopes with mass numbers 209, 210 and 211 can be synthesized. However, all these isotopes decay rapidly (the half-lives of 210 Fr and 211 Fr are three minutes, and 209 Fr is 50 seconds).

Physical and chemical properties

Francium is similar in properties to cesium. Always co-crystallizes with its compounds. Almost all French compounds are water soluble. Relativistic effects 6p-shells make the bond of francium with oxygen in superoxides, for example, of the composition FrO 2, more covalent than superoxides of other alkali metals.

Since researchers have at their disposal only the smallest samples containing no more than 10 −7 g of francium, information on its physical properties can be determined only by calculation, based on data for stable alkali metals. According to these calculations, the density of francium at room temperature is 1.87 g / cm³, the melting point is 27 ° C, the boiling point is 677 ° C, and the specific heat of fusion is 9.385 kJ / kg.

Francium has the lowest electronegativity of all currently known elements. Accordingly, francium is the most reactive alkali metal.

Application

Currently francium and its salts practical application do not have, due to the short half-life and high radioactivity.

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Periodic table of chemical elements of D. I. Mendeleev
	Fr																										Uut		Uup		Uus	Uuo
	Uue	Ubn	Ubu	Ubb	Ubt	Ubq	Ubp	Ubh
Excerpt from France - The commander of the 3rd company to the general! the commander to the general, the 3rd company to the commander! ... - voices were heard in the ranks, and the adjutant ran to find the lingering officer. When the sounds of zealous voices, distorting, shouting "the general in the 3rd company", reached their destination, the required officer appeared from behind the company and, although the man was already elderly and had no habit of running, clinging awkwardly to his socks, trotted towards the general. The captain's face expressed the concern of a schoolboy who was being told to say a lesson he had not learned. There were spots on the red (obviously from intemperance) nose, and the mouth could not find a position. The regimental commander examined the captain from head to toe, while he came up breathlessly, restraining his step as he approached. - You will soon dress people in sundresses! What's this? - shouted the regimental commander, extending his lower jaw and pointing in the ranks of the 3rd company at a soldier in an overcoat of the color of factory cloth, which differed from other overcoats. - Where were you yourself? The commander-in-chief is expected, and you are leaving your place? Huh? ... I will teach you how to dress people in Cossacks for the show! ... Huh? ... The company commander, without taking his eyes off the commander, more and more pressed his two fingers to the visor, as if in this one pressing he now saw his salvation. - Well, why are you silent? Who is there dressed up as a Hungarian? - the regimental commander joked strictly. - Your Excellency… - Well, what about your Excellency? Your Excellency! Your Excellency! Nobody knows what your Excellency is. - Your Excellency, this is Dolokhov, demoted ... - said the captain quietly. - Is he a field marshal, or what, demoted or a soldier? A soldier should be dressed like everyone else, in uniform. - Your Excellency, you yourself allowed him to march. - Allowed? Allowed? You are always like this, young people, - said the regimental commander, cooling down a little. - Allowed? Tell you something, and you and ... - The regimental commander paused. - You say something, and you and ... - What? He said, irritated again. - Please, dress people decently ... And the regimental commander, looking back at the adjutant, with his startling gait went to the regiment. It was evident that he himself liked his irritation, and that, walking around the shelf, he wanted to find another pretext for his anger. Cutting off one officer for an uncleaned sign, another for an incorrect row, he approached the 3rd company. - Kaaak standing? Where is the leg? Where is the leg? - shouted the regimental commander with an expression of suffering in his voice, still a man about five before reaching Dolokhov, dressed in a bluish overcoat. Dolokhov slowly straightened his bent leg and looked straight into the general's face with his bright and insolent gaze. - Why a blue overcoat? Down with ... Feldwebel! Dress him up ... rubbish ... - He did not have time to finish. “General, I am obliged to obey orders, but I am not obliged to endure…” Dolokhov said hastily. - Do not talk at the front! ... Do not talk, do not talk! ... “I’m not obliged to endure insults,” Dolokhov said loudly, sonorously. The general and the soldier's eyes met. The general fell silent, angrily pulling down the tight scarf. “Please change your clothes, please,” he said, walking away. - Rides! - shouted at this time the mahal. The regimental commander blushed, ran up to the horse, took hold of the stirrup with trembling hands, threw his body over, recovered, took out his sword and, with a happy, decisive face, opening his mouth to one side, prepared to shout. The regiment perked up like a recovering bird and froze. - Smir r r r na! - shouted the regimental commander in a tremendous soul voice, joyful for himself, strict in relation to the regiment and friendly in relation to the approaching chief. On a wide, tree-lined, large, roadless road, a tall blue Viennese carriage rode at a rapid trot, slightly rattling with springs. A retinue and a convoy of croats galloped behind the carriage. Near Kutuzov sat an Austrian general in a strange white uniform among the black Russians. The carriage stopped at the regiment. Kutuzov and the Austrian general were quietly talking about something, and Kutuzov smiled slightly, while, stepping heavily, he lowered his foot from the footstep, as if there weren't these 2,000 people who were not looking at him and the regimental commander ... There was a cry of command, again the ringing regiment trembled, making a guard. In the dead silence, the commander-in-chief's faint voice was heard. The regiment barked: "We wish you good health, your fortune!" And again everything froze. At first Kutuzov stood in one place while the regiment moved; then Kutuzov, next to the white general, on foot, accompanied by his retinue, began to walk through the rows. From the way the regimental commander saluted the commander-in-chief, glaring at him, stretching himself out and stealing up, how the leaning forward walked behind the generals through the ranks, barely holding the trembling movement, how he jumped with every word and movement of the commander-in-chief, it was clear that he was fulfilling his duties a subordinate with even greater pleasure than the duties of a boss. The regiment, thanks to the strictness and diligence of the regimental commander, was in excellent condition compared to others who came at the same time to Brownau. There were only 217 retarded and sick people. And everything was fine, except for the shoes. Kutuzov walked through the ranks, occasionally stopping and speaking a few kind words to the officers he knew from the Turkish war, and sometimes to the soldiers. Looking at the shoes, he several times sadly shook his head and pointed at them to the Austrian general with such an expression that, as it were, he did not reproach anyone for this, but he could not help seeing how bad it was. The regimental commander ran ahead each time, fearing to miss the word of the commander-in-chief about the regiment. Behind Kutuzov, at such a distance that every weakly spoken word could be heard, walked about 20 of his suite. The gentlemen of the retinue talked among themselves and sometimes laughed. The handsome adjutant was closest to the commander-in-chief. It was Prince Bolkonsky. Next to him walked his comrade Nesvitsky, a high staff officer, extremely fat, with a kind and smiling handsome face and moist eyes; Nesvitsky could hardly restrain himself from laughing, aroused by the blackish hussar officer walking beside him. The hussar officer, without smiling, without changing the expression of his stopped eyes, looked with a serious face at the back of the regimental commander and mimicked his every movement. Every time the regimental commander shuddered and bent forward, in exactly the same way, the hussar officer shuddered and bent forward. Nesvitsky laughed and pushed others to look at the amusing man.

Francium is an element with an atomic number of 87. The atomic mass of the longest-lived isotope is 223. Francium is a radioactive alkali metal with an extremely pronounced chemical reactivity.

Francium

History of the discovery of france

The metal was discovered back in 1939 by an employee of the Paris Radium Institute named Marguerite Perey. She, apparently, out of patriotic feelings, named the element in honor of her homeland. Francium was discovered while studying the artificially obtained element "actinium": an uncharacteristic radioactive glow was noticed. For the sake of fairness, it should be noted that other researchers could have worked on the creation of this element at the same time, but, as they say, the winners are not judged.

Main characteristics

Today, francium is one of the rarest metals (and indeed chemical elements in general) found in nature.

Earth's crust

According to scientists, the content of this metal in the earth's crust is about 340 grams (only astat is contained less). This is mainly due to his physical instability. Being radioactive, it has a very short half-life (for the most stable isotope it is 22.3 minutes). The only thing that compensates for its natural content is that francium is an intermediate link in the decay of uranium-235 and thorium-232. Thus, all the francium that is found in natural conditions is a product of radioactive decay.

How can you get it?

Let's consider the only way to obtain the most stable isotope of france. This can be done by nuclear reaction of gold with oxygen atoms. All other methods (meaning radioactive decay) are inappropriate, since extremely unstable isotopes are obtained that "live" no more than a few minutes. To get this element at home, like all its compounds, of course, will not work (and there is no need, in fact). many experiments with other metals can be found.

What are the chemical properties of francium?

Francium is similar in properties to cesium. The relativistic effects of the 6p shell ensure that the bond of francium with oxygen in superoxides (for example, of the composition FrO 2) is more covalent relative to superoxides of other elements of this group. Given the lowest electronegativity of all currently existing francium, it is characterized by pronounced chemical activity. All physical properties of this element are indicated only theoretically, since it is not possible to verify them in practice due to the short period of "life" of this element (density \u003d 1.87 g / cm³, melting point \u003d 27 ° C, boiling point \u003d 677 ° C , specific heat of fusion \u003d 9.385 kJ / kg). All compounds of this element are soluble in water (exceptions: salts of perchlorate, chloroplatinate, france picratcobaltinitrite). Francium always co-crystallizes with substances that include cesium. Its coprecipitation with insoluble cesium salts (cesium perchlorate or silicotungstate) is observed. The extraction of france from solutions is carried out:

• chloroplatinates of cesium and rubidium Cs 2 PtCl 6 and Rb 2 PtCl 6;
• chlorobismuthate Cs 2 BiCl 5, chlorostannate Cs 2 SnCl 6 and cesium chloroantimonate Cs 2 SbCl 5 2.5H 2 O;
• free heteropolyacids: silicotungsten and phosphotungsten.

What is the practical significance of this element?

Despite all its uniqueness, francium has not yet been used in practice. Accordingly, it is not used in industry and any technologies. The reason for this is its extremely short half-life. There is evidence that france chloride can be used to diagnose oncological neoplasms, however, in view of the significant cost of this formation, this kind of technique cannot be introduced into systematic use. In principle, cesium has the same properties.

Cesium

So this property of France turned out to be unclaimed: its cost is compared with the cost of a ton of platinum or gold. According to forecasts of leading experts, the element in question will always have a purely cognitive value, nothing more.