Radioactive chemical element. Actinium. Chemical elements. Marie Curie. Radioactive chemical element Magnetic quantum number m l

Actinium

ACTINIUM-I; m.[Greek aktis (aktinos) - ray]. Chemical element (Ac), a silvery-white radioactive metal (found in uranium and thorium ores).

◁ Actinium, oh, oh.

actinium

(lat. Actinium), a chemical element of group III of the periodic table. Radioactive, the most stable isotope is 227 Ac (half-life 21.8 years). Name from Greek. aktís - ray. Silver-white metal, t pl about 1050ºC. Occurs naturally in uranium and thorium ores. A mixture of 227 Ac and 9 Be is a source of neutrons.

ACTINIUM

ACTINIUM (Latin Actinium, from the Greek “actis” - ray), Ac (read “actinium”), a radioactive chemical element with atomic number 89, mass number of the most stable radionuclide actinium 227 (half-life 227 Ac T 1/2 21.8 years). Located in group IIIB, period 7 of the periodic table of elements.
Electronic configuration of the two outer layers of an unexcited actinium atom 6 s 2 p 6 d 1 7s 2 ; oxidation state +3 (valency III). Electronegativity according to Pauling (cm. PAULING Linus) 1,1.
History of discovery
Discovered in 1899 by the French researcher A. Debierne (cm. DEBIERN Andre) in waste from the processing of uranium ore and, independently of him, in 1908 - by F. Gisel.
Being in nature
The content in the earth's crust is about 6·10 -10% by weight. The constant presence of 227 Ac and less stable actinium 228 Ac in the earth's crust is associated with their inclusion in the radioactive series (cm. RADIOACTIVE SERIES) uranium-235 and thorium-232. The rate of formation of these radionuclides is equal to the rate of their radioactive decay, therefore the earth's crust contains constant amounts of these atoms.
Physical and chemical properties
Little studied. Melting point 1050 °C, boiling point 3300 °C. In air, it quickly becomes covered with an oxide film Ac 2 O 3, which prevents the destruction of the metal.
The chemical properties of sea anemone are similar to lanthanum (cm. LANTHANUM). Actinium hydroxide Ac(OH) 3 is a base and has properties similar to alkaline earth hydroxides.
Application
Mixed with beryllium (cm. BERYLLIUM) 227 Ac is used for the manufacture of ampoule sources of neutrons formed when 9 Be nuclei are irradiated by a-particles emitted by 227 Ac. Actinium and its compounds are toxic, MPC 227 Ac 1.310 -6.


encyclopedic Dictionary. 2009 .

Synonyms:

See what “sea anemone” is in other dictionaries:

    - (Greek). The radioactive element, a satellite of zinc, is somewhat similar to thorium. Dictionary of foreign words included in the Russian language. Chudinov A.N., 1910. Sea anemone sea anemones, sea. nettle or lily animals from class. polyps, bright colors... ... Dictionary of foreign words of the Russian language

    - (Ac) radioactive chemical. element III gr. periodic system, serial number 89, mass number of the longest-lived isotope 227. Its abundance in the earth's crust is 6 10 10% by weight. Ac227 is a member of radioactive actinouranium (U235)… … Geological encyclopedia

    - (Actinium), Ac, radioactive chemical element of group III of the periodic table, atomic number 89; metal. Actinium was discovered in 1899 by the French chemist A. Debierne... Modern encyclopedia

    Actinium- (Actinium), Ac, radioactive chemical element of group III of the periodic table, atomic number 89; metal. Actinium was discovered in 1899 by the French chemist A. Debierne. ... Illustrated Encyclopedic Dictionary

    - (lat. Actinium) Ac, chemical element of group III of the periodic table, atomic number 89, atomic mass 227.0278. Radioactive, the most stable isotope is 227Ac (half-life 21.8 years). The name is from the Greek aktis ray. Silvery white... ... Big Encyclopedic Dictionary

    - (from Greek aktis, gender aktinos ray, sparkle, radiance; pat. Actinium), Ac, radioact. chem. element of group III periodic. systems of elements, at. number 89, the first of the elements of the actinide family. Naib. long-lived radioactive isotope 227 Ac... ... Physical encyclopedia

    Noun, number of synonyms: 3 actinide (16) actinouran (1) element (159) Dictionary with ... Synonym dictionary

    Discovered by the Englishman Finson (1881) A new element, a satellite of zinc; its chemical individuality, however, cannot be considered established. F. noticed that in some cases the white precipitate of zinc sulfide darkens in direct sunlight... ... Encyclopedia of Brockhaus and Efron

    ACTINIUM- (from the Greek aktis ray), a radioactive chemical element (at. v. 226). Its ancestor, apparently, is uranium, and the final decay product is actinium lead. The activity of A. itself is halved after 20 years. Lit.: Faience K.,... ... Great Medical Encyclopedia

    actinium- Radio act. element III gr. Periodic systems; at. n. 89. Discovered in 1899 by A. Debierne in the remains of uranium ores after uranium extraction. The longest-lived isotope of the 12 known is 227Ac (T1/2= 21.7 g, P ... Technical Translator's Guide

    89 Radium ← Actinium → Thorium ... Wikipedia

Books

  • Illustrated keys to free-living invertebrates of the Eurasian seas and adjacent deep-sea parts of the Arctic. Volume 3, Sirenko B.I.. The third volume of keys includes scyphoid jellyfish, stauromedusa, siphonophores, hydroid polyps and jellyfish, sea anemones, antipataria, soft corals, ceriantharia. sea ​​feathers, madrepores...
  • Illustrated keys to free-living invertebrates of the Eurasian seas and adjacent deep-sea parts of the Arctic. Volume 3. Cnidarians and Ctenophores,. The third volume of keys includes scyphoid jellyfish, stauromedusa, siphonophores, hydroid polyps and jellyfish, sea anemones, antipataria, soft corals, ceriantharia. sea ​​feathers, madrepores...
You need to enable JavaScript to run this app.

Electronic configuration of an atom is a formula showing the arrangement of electrons in an atom by levels and sublevels. After studying the article, you will learn where and how electrons are located, get acquainted with quantum numbers and be able to construct the electronic configuration of an atom by its number; at the end of the article there is a table of elements.

Why study the electronic configuration of elements?

Atoms are like a construction set: there is a certain number of parts, they differ from each other, but two parts of the same type are absolutely the same. But this construction set is much more interesting than the plastic one and here’s why. The configuration changes depending on who is nearby. For example, oxygen next to hydrogen Maybe

turn into water, when near sodium it turns into gas, and when near iron it completely turns it into rust.

To answer the question of why this happens and predict the behavior of an atom next to another, it is necessary to study the electronic configuration, which will be discussed below.

How many electrons are in an atom?

An atom consists of a nucleus and electrons rotating around it; the nucleus consists of protons and neutrons. In the neutral state, each atom has the number of electrons equal to the number of protons in its nucleus. The number of protons is designated by the atomic number of the element, for example, sulfur has 16 protons - the 16th element of the periodic table. Gold has 79 protons - the 79th element of the periodic table. Accordingly, sulfur has 16 electrons in the neutral state, and gold has 79 electrons.

  • Where to look for an electron?
  • By observing the behavior of the electron, certain patterns were derived; they are described by quantum numbers, there are four in total:
  • Principal quantum number
  • Orbital quantum number

Magnetic quantum number

Further, instead of the word orbit, we will use the term “orbital”; an orbital is the wave function of an electron; roughly, it is the region in which the electron spends 90% of its time.
N - level
L - shell
M l - orbital number
M s - first or second electron in the orbital

Orbital quantum number l

As a result of studying the electron cloud, they found that depending on the energy level, the cloud takes four main forms: a ball, dumbbells and two other, more complex ones.

In order of increasing energy, these forms are called the s-, p-, d- and f-shell.
Each of these shells can have 1 (on s), 3 (on p), 5 (on d) and 7 (on f) orbitals. The orbital quantum number is the shell in which the orbitals are located. The orbital quantum number for the s, p, d and f orbitals takes the values ​​0,1,2 or 3, respectively.
There is one orbital on the s-shell (L=0) - two electrons
There are three orbitals on the p-shell (L=1) - six electrons

There are five orbitals on the d-shell (L=2) - ten electrons

There are seven orbitals on the f-shell (L=3) - fourteen electrons

Magnetic quantum number m l

There are three orbitals on the p-shell, they are designated by numbers from -L to +L, that is, for the p-shell (L=1) there are orbitals “-1”, “0” and “1”.
The magnetic quantum number is denoted by the letter m l.

Inside the shell, it is easier for electrons to be located in different orbitals, so the first electrons fill one in each orbital, and then a pair of electrons is added to each one.

Consider the d-shell:

The d-shell corresponds to the value L=2, that is, five orbitals (-2,-1,0,1 and 2), the first five electrons fill the shell taking the values ​​M l =-2, M l =-1, M l =0 , M l =1,M l =2.

Spin quantum number m s

Spin is the direction of rotation of an electron around its axis, there are two directions, so the spin quantum number has two values: +1/2 and -1/2. One energy sublevel can only contain two electrons with opposite spins. The spin quantum number is denoted m s


So, any electron can be described by four quantum numbers, the combination of these numbers is unique for each position of the electron, take the first electron, the lowest energy level is N = 1, at the first level there is one shell, the first shell at any level has the shape of a ball (s -shell), i.e. L=0, the magnetic quantum number can take only one value, M l =0 and the spin will be equal to +1/2.

If we take the fifth electron (in whatever atom it is), then the main quantum numbers for it will be: N=2, L=1, M=-1, spin 1/2.

This is not the merit of actinium, but nevertheless its place in the periodic table is special.

Actinium
However, we note right away that in none of the works of D.I. Mendeleev, associated with the discovery and development of the periodic law, there is no serious discussion about the element that should occupy the 89th cell in the table. Moreover, even in the last lifetime editions of “Fundamentals of Chemistry”, published already in the 20th century, only a few lines are devoted to sea anemone, and even then only in additions to the 21st chapter. Mendeleev mentions the similarity of actinium with thorium and that this element “is released with thorium and is precipitated before it from both sulfide-sodium salt and hydrogen peroxide.” That's all! Perhaps none of the elements discovered by that time was given so little space in the “Fundamentals of Chemistry”. There were reasons for this.

Ten years after the discovery of actinium, the famous English physicist Frederick Soddy ingeniously systematized the complex of information accumulated by that time about element N° 89. Here it is:

“Atomic weight is unknown; average life expectancy is unknown; nature of radiation - does not emit rays; parent substance - unknown; the starting material is probably uranium; the decay product is radioactinium.” polonium polonium radium radium

Few people know about this scientist in our country. Let's try to fill this gap, at least to a small extent. Debierne became an employee of the Curies when he was a very young man: he was about 25 years old. His biggest discovery is. In addition, he, together with Marie Skłodowska-Curie, obtained the first sample of metallic radium in 1910. That same year they confirmed the discovery of polonium. After the death of Marie Skłodowska-Curie, Debierne headed the Pierre Curie Laboratory at the Radium Institute in Paris.

The following lines were preserved in the notes of Marie Sklodowska-Curie: “Around 1900, Pierre Curie met the young chemist Andre Debierne, who worked as a preparator for Professor Friedel, who greatly valued him as a scientist. Andre Debierne readily agreed to Pierre's proposal to study radioactivity: he undertook research on a new radioelement, the existence of which was suspected in the group gland and rare earths. He discovered this element, called actinium (emphasis in the original - Ed.). Although Andre Debierne worked in the chemical and physical laboratory of the Sorbonne University, headed by Jean Perrin, he often came to our barn, soon becoming a very close friend of both ours and Dr. Curie, and subsequently our children.”

What did this young chemist do in the fall of 1899? Exploring the remains uranium tar, from which both radium and polonium had already been removed, he detected weak radiation. So the famous tar contained another new element? Such an assumption after the discovery of radium and polonium seemed natural and undeniable. Debierne proposed to call this element actinium (or Greek autk; - “radiation, light”) by analogy with radium. Attempts were made to isolate the new element, but they were unsuccessful, and Debierne, along with the Curies, concentrated on radium.

A little over a year later, from the same fraction of uranium tar containing rare earths, the German researcher F. Gnzel obtained a highly emitting solution. He even managed (it took enormous effort) to free this solution from many impurities and obtain a relatively pure emitter - in fact, the first actinium preparation. But Gnzel did not know this: he believed that he had discovered a new element, and called it emanation. But soon the identity of emanium and sea anemone was proven, and the new element “did not take place.”

The most unusual thing here is probably that the element called “radiating” (that’s how the name “sea anemone” is literally translated) could not actually be discovered by its radiation. As is now known, the longest-lived natural isotope of actinium, 227Ac, ​​decays in the vast majority of cases, emitting very soft, low-energy beta rays. The recording equipment that existed at the turn of the 19th and 20th centuries could not detect this radiation. It was impossible to use it to register those rare (approximately 1.2%) cases when these nuclei decayed, emitting alpha particles. Both Debierne and Giesel discovered element No. 89 not by its own radiation, but by the radiation of its daughter products: in fact, they observed the radiation of an isotope of the already known thorium.

But new activity was associated with lanthanum and its family. There was free space in the periodic table for an analogue of lanthanum, a heavy radioactive element of group III. This is where sea anemone was identified. And they were not mistaken.

Actinium is indeed similar to lanthanum. They have very similar chemical properties: common valency (3+), close atomic radii (1.87 and 2.03 A°), almost identical structure of most compounds. Like lanthanum, most actinium salts are white; Ac203 oxide too. And the fact that actinium is superior to lanthanum in chemical activity is quite natural; it is a heavier metal analogue: valence electrons circulate further from the nucleus. However, when it comes to the valence of lanthanum, actinium and their families, another question is which electrons are the most important...

But by providing the reader with this information, we have clearly gotten ahead of ourselves. Talking about compounds before talking about the physical properties of the element itself is at least unusual. But the physical properties of actinium were reliably determined only in the 50s, and there were reasons for that too.

Actinium exists in nature. It, its main and longest-lived isotope 227 Ac, is formed during the decay of uranium-235. The amount of anemone produced is so small that this element is definitely one of the ten rarest elements on Earth. Its content in the earth's crust is determined by ten billionths of a percent. It is estimated that all earthly minerals contain only 2600 tons of actinium, and radium (the extreme difficulty of extracting which is known not only from the works of Curie, but also from the poems of Mayakovsky) - approximately 40-50 million tons.

Actinium - methods of obtaining

Extraction of actinium from natural sources ( uranium minerals) is further complicated by its extreme similarity to elements of the rare earth family. The famous French radiochemist M. Gaisinsky wrote: “In some processes, actinium is separated from lanthanum, and in others it follows lanthanum. However, during the fractional crystallization of double lanthanide nitrates with magnesium or manganese sea ​​anemone is not isolated in the first fraction before lanthanum, but is concentrated between neodymium polonium samarium. This anomaly has not yet been explained. Currently, the preferred method for producing actinium is irradiation of radium with neutrons.” Here's what's happening here:

226 88 Ra + 10n → 227 88 Ra - β → 227 89 Ac

Obviously, it is easier to separate divalent radium and trivalent actinium than to isolate the same actinium from a mixture of lanthanum and its analogues. And the half-life of radium-227 is short - only 41 minutes. Therefore, the fastest and cheapest way (if it is at all appropriate to talk about cheapness here) is to obtain sea anemone from super-precious radium. It was in this way that pure preparations of element No. 89 were obtained, on which its main properties were determined. Elemental sea anemone turned out to be a silvery-white metal, quite heavy (density slightly more than 10 g/cm3) and very chemically active. Its melting point, determined experimentally, is 1040±50°C, and its boiling point, calculated theoretically, is about 3200°C.

In air, sea anemones are oxidized to Ac2O3. By the way, metal actinium (in milligram quantities) was obtained in two ways: by reducing AcC13 in pairs potassium at 350°C and from trifluoride, acting on it as a vapor lithium. In the latter case, a higher temperature was required - over 1000 ° C, but the resulting samples were cleaner.

There are now 24 known isotopes of actinium, three of which occur in nature. These are relatively long-lived actinium-227, actinium-228 (aka mesothorium-P) with a half-life of 6.13 hours, and actinium-225 with a half-life of about 10 days. The remaining isotopes are artificial: most of them are obtained by bombarding thorium with various particles.

The practical use of actinium is limited to neutron sources. Neutrons in them are formed during irradiation beryllium-9 alpha particles. And alpha particles are produced by the daughter products of actinium-227. There is reason to believe that actinium-beryllium neutron sources are by no means the best or most economical of such devices.
But this does not mean that sea anemone is useless. The study of actinium has given a lot to science, and especially nuclear physics. Let us note right away that actinometry (an important branch of geophysics) has as little connection with the study of actinium as sea anemones (sea inhabitants) or actinomycins (antibiotics). But sea anemone is the basis for the famous actinoid theory of G. Seaborg, and if sea anemones can exist without actinium, then without this element this theory would not exist. Element France also would not have been discovered if not for sea anemone. More precisely, if actinium-227 did not decay in two ways and did not sometimes (on average in 12 cases out of 1000) transform into francium-223.

The study of this element will still bring a lot of new things to science. Physicists, for example, still cannot explain why the most famous and most studied isotope of element No. 89, actinium-227, has a variable half-life. Produced artificially from radium or formed by the alpha decay of pure protactinium-231, it has a half-life of 21.8 years, while isolated from actinium-containing minerals it has a much shorter half-life. Chemists continue to debate the possibility of the existence of monovalent actinium compounds. It seems that, according to existing ideas about the electronic configuration of its atom, there should be such compounds, but they cannot be obtained in any way!

In a word, sea anemone will not soon be considered a well-studied “textbook” element. In the meantime, like the firefly from the famous children's story, “he is alive and glowing.” True, it glows not as brightly as radium, but it glows...

The chemical element with atomic number 89 is designated in the periodic table of elements by the symbol Ac(lat. Actinium, from the Greek “aktis” - ray). There are 3 isotopes of actinium found in nature: 225Ac, 227Ac, ​​228Ac(all of them are unstable). There are also 24 isotopes of actinium obtained artificially. The atomic radius of actinium is 1.88 A.

Actinium accompanies uranium ores. Its contents in natural ores corresponds to equilibrium. Increased amounts of actinium are found in molybdenite, chalcopyrite, cassiterite, quartz, and pyrolusite. It is characterized by low migration ability in natural objects. Actinium is one of the least abundant radioactive elements in nature. Its total content in the earth’s crust does not exceed 2600 tons, while, for example, the amount of radium is more than 40 million tons.

silver-white metal, resembles lanthanum in appearance. Due to radioactivity, it glows in the dark with a characteristic blue color. It can exist in two crystalline forms, but only one form has been obtained - beta-Ac, which has a face-centered cubic structure. It was not possible to obtain the low-temperature alpha form. was opened in October 1899 by A. Debierne in waste from the processing of uranium tar, from which polonium and radium were removed. Andre Debierne was one of the few willing assistants of Pierre and Marie Curie in their research into radioactive elements. Few people know about this scientist in our country.

He became an employee of the Curies when he was a very young man: he was about 25 years old. His biggest discovery was sea anemone. In addition, he, together with Marie Skłodowska-Curie, obtained the first sample of metallic radium in 1910. That same year they confirmed the discovery of polonium. After the death of Marie Skłodowska-Curie, Debierne headed the Pierre Curie Laboratory at the Paris Institute of Radium. Examining the remains of uranium tar, from which both radium and polonium had already been removed, he discovered weak radiation. Debierne proposed calling this element actinium (from the Greek - “radiation, light”) by analogy with radium. Attempts were made to isolate the new element, but they were unsuccessful, and Debierne, along with the Curies, concentrated on radium. Soon after Debierne's discovery, independently of him, the German radiophysicist F. Giesel obtained a highly radioactive element from the same fraction of uranium tar containing rare earth elements and proposed the name "emanium" for it. Further research showed the identity of the preparations obtained by Debierne and Giesel, although they observed radioactive radiation not from actinium itself, but from its decay products - 227Th (radioactinium) and 230Th (ionium). Actinium is one of the dangerous radioactive poisons

with high specific alpha activity. Although the absorption of actinium from the digestive tract is relatively small compared to radium, the most important feature of actinium is its ability to be firmly retained in the body in the surface layers of bone tissue. Initially, sea anemone accumulates to a large extent in the liver, and the rate of its removal from the body is much greater than the rate of its radioactive decay. In addition, one of the daughter products of its decay is very dangerous radon, protection against which when working with actinium is a separate serious task. sea ​​anemone is limited by neutron sources. Neutrons in them are formed when beryllium-9 is irradiated with alpha particles. And alpha particles are produced by the daughter products of actinium-227. There is reason to believe that actinium-beryllium neutron sources are by no means the best or most economical of such devices. But this does not mean that sea anemone is useless. The study of actinium has given a lot to science, and especially nuclear physics. Let us note right away that actinometry (an important branch of geophysics) has as little connection with the study of actinium as sea anemones (sea inhabitants) or actinomycins (antibiotics). But the famous actinoid theory of G. Seaborg is based on sea anemones, and if sea anemones can exist without actinium, then without this element this theory would not exist. The element francium would also not have been discovered if it were not for sea anemone. More precisely, if actinium-227 did not decay in two ways and did not sometimes (on average in 12 cases out of 1000) transform into francium-223.

Studying This element will still bring a lot of new things to science. Physicists, for example, still cannot explain why the most famous and most studied isotope of element No. 89, actinium-227, has a variable half-life. Produced artificially from radium or formed by the alpha decay of pure protactinium-231, it has a half-life of 21.8 years, while isolated from actinium-containing minerals it has a much shorter half-life. Chemists continue to debate the possibility of the existence of monovalent actinium compounds. It seems that, according to existing ideas about the electronic configuration of its atom, there should be such compounds, but they cannot be obtained in any way!

In a word, sea anemone will not soon be considered a well-studied “textbook” element. In the meantime, like the firefly from the famous children's story, “he is alive and glowing.” True, it glows not as brightly as radium, but it glows...

The article is based on material from the book "Popular Library of Chemical Elements". Publishing house "Science", 1977. (electronic version of the book -