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98-629: The disposal method consists of the following steps: If the holes into the rock from the tunnel are drilled vertically, the method is called KBS-3V and if they are drilled horizontally it is called KBS-3H. The only method considered so far is KBS-3V. The overall theory is that radioactive rock has always been present in the earth, and it is generally harmless to human populations. Further, Cigar Lake and Oklo have proven that actinides do not easily migrate via ground water or other means. Spent fuel consists of radioactive ceramic, cooled until its short-half-life radioactives have decayed, so its heat-production

196-444: A magnetic field . Electrons, due to their smaller mass and thus larger space-filling properties as matter waves , determine the size of atoms and molecules that possess any electrons at all. Thus, anions (negatively charged ions) are larger than the parent molecule or atom, as the excess electron(s) repel each other and add to the physical size of the ion, because its size is determined by its electron cloud . Cations are smaller than

294-437: A particle accelerator . Thus nobelium was produced by bombarding uranium-238 with neon-22 as The first isotopes of transplutonium elements, americium-241 and curium-242 , were synthesized in 1944 by Glenn T. Seaborg , Ralph A. James and Albert Ghiorso . Curium-242 was obtained by bombarding plutonium-239 with 32-MeV α-particles: The americium-241 and curium-242 isotopes also were produced by irradiating plutonium in

392-429: A primordial nuclide . The next longest-lived is Th, an intermediate decay product of U with a half-life of 75,400 years. Several other thorium isotopes have half-lives over a day; all of these are also transient in the decay chains of Th, U, and U. Twenty-nine isotopes of protactinium are known with mass numbers 211–239 as well as three excited isomeric states . Only Pa and Pa have been found in nature. All

490-454: A free electron and a positive ion. Ions are also created by chemical interactions, such as the dissolution of a salt in liquids, or by other means, such as passing a direct current through a conducting solution, dissolving an anode via ionization . The word ion was coined from neuter present participle of Greek ἰέναι ( ienai ), meaning "to go". A cation is something that moves down ( Greek : κάτω , kato , meaning "down") and an anion

588-415: A gas is extensively used for the detection of radiation such as alpha , beta , gamma , and X-rays . The original ionization event in these instruments results in the formation of an "ion pair"; a positive ion and a free electron, by ion impact by the radiation on the gas molecules. The ionization chamber is the simplest of these detectors, and collects all the charges created by direct ionization within

686-400: A gas with less net electric charge is called the ionization potential , or ionization energy . The n th ionization energy of an atom is the energy required to detach its n th electron after the first n − 1 electrons have already been detached. Each successive ionization energy is markedly greater than the last. Particularly great increases occur after any given block of atomic orbitals

784-589: A half-life of 77 minutes. Another alpha emitter, Md, has a half-life of 53 days. Both these isotopes are produced from rare einsteinium ( Es and Es respectively), that therefore limits their availability. Long-lived isotopes of nobelium and isotopes of lawrencium (and of heavier elements) have relatively short half-lives. For nobelium, 13 isotopes are known, with mass numbers 249–260 and 262. The chemical properties of nobelium and lawrencium were studied with No (t 1/2  = 3 min) and Lr (t 1/2  = 35 s). The longest-lived nobelium isotope, No, has

882-708: A half-life of approximately 1 hour. Lawrencium has 14 known isotopes with mass numbers 251–262, 264, and 266. The most stable of them is Lr with a half life of 11 hours. Among all of these, the only isotopes that occur in sufficient quantities in nature to be detected in anything more than traces and have a measurable contribution to the atomic weights of the actinides are the primordial Th, U, and U, and three long-lived decay products of natural uranium, Th, Pa, and U. Natural thorium consists of 0.02(2)% Th and 99.98(2)% Th; natural protactinium consists of 100% Pa; and natural uranium consists of 0.0054(5)% U, 0.7204(6)% U, and 99.2742(10)% U. The figure buildup of actinides

980-490: A long arrow pointing down-left. A few long-lived actinide isotopes, such as Pu and Cm, cannot be produced in reactors because neutron capture does not happen quickly enough to bypass the short-lived beta-decaying nuclides Pu and Cm; they can however be generated in nuclear explosions, which have much higher neutron fluxes. Thorium and uranium are the most abundant actinides in nature with the respective mass concentrations of 16 ppm and 4 ppm. Uranium mostly occurs in

1078-483: A minus indication "Anion (−)" indicates the negative charge. With a cation it is just the opposite: it has fewer electrons than protons, giving it a net positive charge, hence the indication "Cation (+)". Since the electric charge on a proton is equal in magnitude to the charge on an electron, the net electric charge on an ion is equal to the number of protons in the ion minus the number of electrons. An anion (−) ( / ˈ æ n ˌ aɪ . ən / ANN -eye-ən , from

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1176-440: A molecule/atom with multiple charges is by drawing out the signs multiple times, this is often seen with transition metals. Chemists sometimes circle the sign; this is merely ornamental and does not alter the chemical meaning. All three representations of Fe , Fe , and Fe shown in the figure, are thus equivalent. Monatomic ions are sometimes also denoted with Roman numerals , particularly in spectroscopy ; for example,

1274-402: A neutral atom or molecule is called ionization . Atoms can be ionized by bombardment with radiation , but the more usual process of ionization encountered in chemistry is the transfer of electrons between atoms or molecules. This transfer is usually driven by the attaining of stable ("closed shell") electronic configurations . Atoms will gain or lose electrons depending on which action takes

1372-462: A nuclear reactor. The latter element was named after Marie Curie and her husband Pierre who are noted for discovering radium and for their work in radioactivity . Bombarding curium-242 with α-particles resulted in an isotope of californium Cf in 1950, and a similar procedure yielded berkelium-243 from americium-241 in 1949. The new elements were named after Berkeley, California , by analogy with its lanthanide homologue terbium , which

1470-592: A positive charge, forming the ion NH + 3 . However, this ion is unstable, because it has an incomplete valence shell around the nitrogen atom, making it a very reactive radical ion. Due to the instability of radical ions, polyatomic and molecular ions are usually formed by gaining or losing elemental ions such as H , rather than gaining or losing electrons. This allows the molecule to preserve its stable electronic configuration while acquiring an electrical charge. The energy required to detach an electron in its lowest energy state from an atom or molecule of

1568-411: A precise ionic gradient across membranes , the disruption of this gradient contributes to cell death. This is a common mechanism exploited by natural and artificial biocides , including the ion channels gramicidin and amphotericin (a fungicide ). Inorganic dissolved ions are a component of total dissolved solids , a widely known indicator of water quality . The ionizing effect of radiation on

1666-467: A rarely used wide-formatted periodic table inserts the 4f and 5f series in their proper places, as parts of the table's sixth and seventh rows (periods). Primordial   From decay   Synthetic   Border shows natural occurrence of the element Like the lanthanides , the actinides form a family of elements with similar properties. Within the actinides, there are two overlapping groups: transuranium elements , which follow uranium in

1764-509: A rather high rate of spontaneous fission. Cm has the longest lifetime among isotopes of curium (1.56 × 10 years), but is not formed in large quantities because of the strong fission induced by thermal neutrons. Seventeen isotopes of berkelium have been identified with mass numbers 233, 234, 236, 238, and 240–252. Only Bk is available in large quantities; it has a relatively short half-life of 330 days and emits mostly soft β-particles , which are inconvenient for detection. Its alpha radiation

1862-552: A series of beta decays to nuclides such as einsteinium-253 and fermium-255 . The discovery of the new elements and the new data on neutron capture were initially kept secret on the orders of the US ;military until 1955 due to Cold War tensions. Nevertheless, the Berkeley team were able to prepare einsteinium and fermium by civilian means, through the neutron bombardment of plutonium-239, and published this work in 1954 with

1960-406: A short half-life (hours), which can be isolated in significant amounts. Fm (t 1/2 = 100 days) can accumulate upon prolonged and strong irradiation. All these isotopes are characterized by high rates of spontaneous fission. Among the 17 known isotopes of mendelevium (mass numbers from 244 to 260), the most studied is Md, which mainly decays through electron capture (α-radiation is ≈10%) with

2058-414: A stable configuration. This property is known as electropositivity . Non-metals, on the other hand, are characterized by having an electron configuration just a few electrons short of a stable configuration. As such, they have the tendency to gain more electrons in order to achieve a stable configuration. This tendency is known as electronegativity . When a highly electropositive metal is combined with

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2156-427: A yellow colour, and beta emitters have a blue colour. Pink indicates electron capture ( Np), whereas white stands for a long-lasting metastable state ( Am). The formation of actinide nuclides is primarily characterised by: In addition to these neutron- or gamma-induced nuclear reactions , the radioactive conversion of actinide nuclides also affects the nuclide inventory in a reactor. These decay types are marked in

2254-401: A −2 charge is known as a dianion and an ion with a +2 charge is known as a dication . A zwitterion is a neutral molecule with positive and negative charges at different locations within that molecule. Cations and anions are measured by their ionic radius and they differ in relative size: "Cations are small, most of them less than 10 m (10 cm) in radius. But most anions are large, as is

2352-406: Is Pu with half-life of 8.13 × 10 years. Eighteen isotopes of americium are known with mass numbers from 229 to 247 (with the exception of 231). The most important are Am and Am, which are alpha-emitters and also emit soft, but intense γ-rays; both of them can be obtained in an isotopically pure form. Chemical properties of americium were first studied with Am, but later shifted to Am, which

2450-527: Is a d-block element and a transition metal . The series mostly corresponds to the filling of the 5f electron shell , although as isolated atoms in the ground state many have anomalous configurations involving the filling of the 6d shell due to interelectronic repulsion. In comparison with the lanthanides , also mostly f-block elements, the actinides show much more variable valence . They all have very large atomic and ionic radii and exhibit an unusually large range of physical properties. While actinium and

2548-914: Is a β-emitter with a half-life of 26.97 days. There are 27 known isotopes of uranium , having mass numbers 215–242 (except 220). Three of them, U , U and U, are present in appreciable quantities in nature. Among others, the most important is U, which is a final product of transformation of Th irradiated by slow neutrons. U has a much higher fission efficiency by low-energy (thermal) neutrons, compared e.g. with U. Most uranium chemistry studies were carried out on uranium-238 owing to its long half-life of 4.4 × 10 years. There are 25 isotopes of neptunium with mass numbers 219–244 (except 221); they are all highly radioactive. The most popular among scientists are long-lived Np (t 1/2  = 2.20 × 10 years) and short-lived Np, Np (t 1/2  ~ 2 days). There are 21 known isotopes of plutonium , having mass numbers 227–247. The most stable isotope of plutonium

2646-428: Is a member of the radioactive thorium series formed by the decay of Ra ; it is a β emitter with a half-life of 6.15 hours. In one tonne of thorium there is 5 × 10 gram of Ac. It was discovered by Otto Hahn in 1906. There are 32 known isotopes of thorium ranging in mass number from 207 to 238. Of these, the longest-lived is Th, whose half-life of 1.4 × 10  years means that it still exists in nature as

2744-416: Is a negatively charged ion with more electrons than protons. (e.g. Cl (chloride ion) and OH (hydroxide ion)). Opposite electric charges are pulled towards one another by electrostatic force , so cations and anions attract each other and readily form ionic compounds . If only a + or - is present, it indicates a +1 or -1 charge. To indicate a more severe charge, the number of additional or missing atoms

2842-414: Is a table of nuclides with the number of neutrons on the horizontal axis (isotopes) and the number of protons on the vertical axis (elements). The red dot divides the nuclides in two groups, so the figure is more compact. Each nuclide is represented by a square with the mass number of the element and its half-life. Naturally existing actinide isotopes (Th, U) are marked with a bold border, alpha emitters have

2940-415: Is a β-emitter and the rest are α-emitters. The isotopes with even mass numbers ( Cf, Cf and Cf) have a high rate of spontaneous fission, especially Cf of which 99.7% decays by spontaneous fission. Californium-249 has a relatively long half-life (352 years), weak spontaneous fission and strong γ-emission that facilitates its identification. Cf is not formed in large quantities in a nuclear reactor because of

3038-439: Is almost 20 times less radioactive. The disadvantage of Am is production of the short-lived daughter isotope Np, which has to be considered in the data analysis. Among 19 isotopes of curium , ranging in mass number from 233 to 251, the most accessible are Cm and Cm; they are α-emitters, but with much shorter lifetime than the americium isotopes. These isotopes emit almost no γ-radiation, but undergo spontaneous fission with

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3136-484: Is an atom or molecule with a net electrical charge . The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton , which is considered to be positive by convention. The net charge of an ion is not zero because its total number of electrons is unequal to its total number of protons. A cation is a positively charged ion with fewer electrons than protons (e.g. K (potassium ion)) while an anion

3234-429: Is exhausted of electrons. For this reason, ions tend to form in ways that leave them with full orbital blocks. For example, sodium has one valence electron in its outermost shell, so in ionized form it is commonly found with one lost electron, as Na . On the other side of the periodic table, chlorine has seven valence electrons, so in ionized form it is commonly found with one gained electron, as Cl . Caesium has

3332-615: Is in the breakdown of adenosine triphosphate ( ATP ), which provides the energy for many reactions in biological systems. Ions can be non-chemically prepared using various ion sources , usually involving high voltage or temperature. These are used in a multitude of devices such as mass spectrometers , optical emission spectrometers , particle accelerators , ion implanters , and ion engines . As reactive charged particles, they are also used in air purification by disrupting microbes, and in household items such as smoke detectors . As signalling and metabolism in organisms are controlled by

3430-426: Is more important for applications, as only neutron irradiation using nuclear reactors allows the production of sizeable amounts of synthetic actinides; however, it is limited to relatively light elements. The advantage of the second method is that elements heavier than plutonium, as well as neutron-deficient isotopes, can be obtained, which are not formed during neutron irradiation. In 1962–1966, there were attempts in

3528-434: Is negligible. When initially made, the ceramic fuel is also wrapped in sealed tubes of corrosion-resistant zirconium alloy . Therefore, spent fuel is not water-soluble in any conventional sense, and is mechanically sturdy. The other elements present (crystalline bedrock, corrosion-resistant copper cylinders, etc.) have been scientifically proven to reduce the exposure to ground water, and the rate at which it can penetrate to

3626-601: Is not affected by the weak Ac migration. Protactinium is more abundant (10 %) in the Earth's crust than actinium. It was discovered in uranium ore in 1913 by Fajans and Göhring. As actinium, the distribution of protactinium follows that of U. The half-life of the longest-lived isotope of neptunium, Np , is negligible compared to the age of the Earth. Thus neptunium is present in nature in negligible amounts produced as intermediate decay products of other isotopes. Traces of plutonium in uranium minerals were first found in 1942, and

3724-607: Is one short of the stable, filled shell with 8 electrons. Thus, a chlorine atom tends to gain an extra electron and attain a stable 8- electron configuration , becoming a chloride anion in the process: This driving force is what causes sodium and chlorine to undergo a chemical reaction, wherein the "extra" electron is transferred from sodium to chlorine, forming sodium cations and chloride anions. Being oppositely charged, these cations and anions form ionic bonds and combine to form sodium chloride , NaCl, more commonly known as table salt. Polyatomic and molecular ions are often formed by

3822-451: Is possible to mix the notations for the individual metal centre with a polyatomic complex, as shown by the uranyl ion example. If an ion contains unpaired electrons , it is called a radical ion. Just like uncharged radicals, radical ions are very reactive. Polyatomic ions containing oxygen, such as carbonate and sulfate, are called oxyanions . Molecular ions that contain at least one carbon to hydrogen bond are called organic ions . If

3920-547: Is rather weak (1.45 × 10 % with respect to β-radiation), but is sometimes used to detect this isotope. Bk is an alpha-emitter with a long half-life of 1,380 years, but it is hard to obtain in appreciable quantities; it is not formed upon neutron irradiation of plutonium because β-decay of curium isotopes with mass number below 248 is not known. ( Cm would actually release energy by β-decaying to Bk, but this has never been seen.) The 20 isotopes of californium with mass numbers 237–256 are formed in nuclear reactors; californium-253

4018-473: Is something that moves up ( Greek : ἄνω , ano , meaning "up"). They are so called because ions move toward the electrode of opposite charge. This term was introduced (after a suggestion by the English polymath William Whewell ) by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday did not know

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4116-415: Is supplied, as seen in O 2 (negative charge, peroxide ) and He (positive charge, alpha particle ). Ions consisting of only a single atom are termed atomic or monatomic ions , while two or more atoms form molecular ions or polyatomic ions . In the case of physical ionization in a fluid (gas or liquid), "ion pairs" are created by spontaneous molecule collisions, where each generated pair consists of

4214-432: Is written in superscript immediately after the chemical structure for the molecule/atom. The net charge is written with the magnitude before the sign; that is, a doubly charged cation is indicated as 2+ instead of +2 . However, the magnitude of the charge is omitted for singly charged molecules/atoms; for example, the sodium cation is indicated as Na and not Na . An alternative (and acceptable) way of showing

4312-556: The Fe (positively doubly charged) example seen above is referred to as Fe(III) , Fe or Fe III (Fe I for a neutral Fe atom, Fe II for a singly ionized Fe ion). The Roman numeral designates the formal oxidation state of an element, whereas the superscripted Indo-Arabic numerals denote the net charge. The two notations are, therefore, exchangeable for monatomic ions, but the Roman numerals cannot be applied to polyatomic ions. However, it

4410-402: The environment ; analysis of debris from a 1952 hydrogen bomb explosion showed the presence of americium, curium , berkelium , californium , einsteinium and fermium . In presentations of the periodic table , the f-block elements are customarily shown as two additional rows below the main body of the table. This convention is entirely a matter of aesthetics and formatting practicality;

4508-518: The periodic table ; and transplutonium elements, which follow plutonium. Compared to the lanthanides, which (except for promethium ) are found in nature in appreciable quantities, most actinides are rare. Most do not occur in nature, and of those that do, only thorium and uranium do so in more than trace quantities. The most abundant or easily synthesized actinides are uranium and thorium, followed by plutonium, americium, actinium, protactinium, neptunium, and curium. The existence of transuranium elements

4606-473: The 18 known isotopes of einsteinium with mass numbers from 240 to 257, the most affordable is Es. It is an α-emitter with a half-life of 20.47 days, a relatively weak γ-emission and small spontaneous fission rate as compared with the isotopes of californium. Prolonged neutron irradiation also produces a long-lived isotope Es (t 1/2  = 275.5 days). Twenty isotopes of fermium are known with mass numbers of 241–260. Fm, Fm and Fm are α-emitters with

4704-609: The 60-inch cyclotron of Berkeley Radiation Laboratory ; this was the first isotope of any element to be synthesized one atom at a time. There were several attempts to obtain isotopes of nobelium by Swedish (1957) and American (1958) groups, but the first reliable result was the synthesis of No by the Russian group of Georgy Flyorov in 1965, as acknowledged by the IUPAC in 1992. In their experiments, Flyorov et al. bombarded uranium-238 with neon-22. In 1961, Ghiorso et al. obtained

4802-425: The Earth's crust as a mixture of its oxides in the mineral uraninite , which is also called pitchblende because of its black color. There are several dozens of other uranium minerals such as carnotite (KUO 2 VO 4 ·3H 2 O) and autunite (Ca(UO 2 ) 2 (PO 4 ) 2 ·nH 2 O). The isotopic composition of natural uranium is U (relative abundance 99.2742%), U (0.7204%) and U (0.0054%); of these U has

4900-541: The Greek word ἄνω ( ánō ), meaning "up" ) is an ion with more electrons than protons, giving it a net negative charge (since electrons are negatively charged and protons are positively charged). A cation (+) ( / ˈ k æ t ˌ aɪ . ən / KAT -eye-ən , from the Greek word κάτω ( kátō ), meaning "down" ) is an ion with fewer electrons than protons, giving it a positive charge. There are additional names used for ions with multiple charges. For example, an ion with

4998-476: The United States (440,000 tonnes), Australia and India (~300,000 tonnes each) and Canada (~100,000 tonnes). The abundance of actinium in the Earth's crust is only about 5 × 10 %. Actinium is mostly present in uranium-containing, but also in other minerals, though in much smaller quantities. The content of actinium in most natural objects corresponds to the isotopic equilibrium of parent isotope U, and it

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5096-410: The United States to produce transplutonium isotopes using a series of six underground nuclear explosions . Small samples of rock were extracted from the blast area immediately after the test to study the explosion products, but no isotopes with mass number greater than 257 could be detected, despite predictions that such isotopes would have relatively long half-lives of α-decay . This non-observation

5194-712: The assessments of long-term safety performed by SKB and Posiva. The first facilities using this method will be located in Östhammar , Sweden , next to the Forsmark Nuclear Power Plant , and in Eurajoki , Finland , at the Onkalo spent nuclear fuel repository next to the Olkiluoto Nuclear Power Plant . In 2019, Posiva Ltd. announced that the construction of the spent nuclear fuel handling facility for Onkalo and installation of

5292-448: The associated emission of neutrons. More long-lived isotopes of curium ( Cm, all α-emitters) are formed as a mixture during neutron irradiation of plutonium or americium. Upon short irradiation, this mixture is dominated by Cm, and then Cm begins to accumulate. Both of these isotopes, especially Cm, have a longer half-life (3.48 × 10 years) and are much more convenient for carrying out chemical research than Cm and Cm, but they also have

5390-519: The charge in an organic ion is formally centred on a carbon, it is termed a carbocation (if positively charged) or carbanion (if negatively charged). Monatomic ions are formed by the gain or loss of electrons to the valence shell (the outer-most electron shell) in an atom. The inner shells of an atom are filled with electrons that are tightly bound to the positively charged atomic nucleus , and so do not participate in this kind of chemical interaction. The process of gaining or losing electrons from

5488-449: The contents of the repository are at least as safe as natural deposits of uranium. The process has been extensively studied and depends on well-understood chemistry and geology. The risk of waste disposal is difficult to measure due to the necessity of gathering data over thousands of years. However, by employing process knowledge and risk management methodology, the risk associated with KBS-3 repositories have been thoroughly investigated in

5586-546: The copper capsules of KBS-3 are not as corrosion-proof as SKB and Posiva claim. In response, STUK (the Finnish nuclear safety office) asked Posiva for further explanation. Posiva dismissed the independent research in Sweden and Finland, referring to its own safety studies. SKB undertook follow-up studies, which indicated that the corrosion process does not exist, and that the initial experiments were not correctly executed and/or

5684-409: The corresponding parent atom or molecule due to the smaller size of the electron cloud. One particular cation (that of hydrogen) contains no electrons, and thus consists of a single proton – much smaller than the parent hydrogen atom. Anion (−) and cation (+) indicate the net electric charge on an ion. An ion that has more electrons than protons, giving it a net negative charge, is named an anion, and

5782-566: The disclaimer that it was not the first studies that had been carried out on those elements. The "Ivy Mike" studies were declassified and published in 1955. The first significant (submicrogram) amounts of einsteinium were produced in 1961 by Cunningham and colleagues, but this has not been done for fermium yet. The first isotope of mendelevium, Md (half-life 87 min), was synthesized by Albert Ghiorso, Glenn T. Seaborg, Gregory Robert Choppin , Bernard G. Harvey and Stanley Gerald Thompson when they bombarded an Es target with alpha particles in

5880-419: The figure by diagonal arrows. The beta-minus decay , marked with an arrow pointing up-left, plays a major role for the balance of the particle densities of the nuclides. Nuclides decaying by positron emission (beta-plus decay) or electron capture (ϵ) do not occur in a nuclear reactor except as products of knockout reactions; their decays are marked with arrows pointing down-right. Due to the long half-lives of

5978-428: The first californium compound (0.3 μg of CfOCl) was obtained in 1960 by B. B. Cunningham and J. C. Wallmann. Einsteinium and fermium were identified in 1952–1953 in the fallout from the " Ivy Mike " nuclear test (1 November 1952), the first successful test of a hydrogen bomb. Instantaneous exposure of uranium-238 to a large neutron flux resulting from the explosion produced heavy isotopes of uranium, which underwent

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6076-680: The first element in the series, actinium. The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide. The 1985 IUPAC Red Book recommends that actinoid be used rather than actinide , since the suffix -ide normally indicates a negative ion . However, owing to widespread current use, actinide is still allowed. Since actinoid literally means actinium-like (cf. humanoid or android ), it has been argued for semantic reasons that actinium cannot logically be an actinoid, but IUPAC acknowledges its inclusion based on common usage. Actinium through nobelium are f-block elements, while lawrencium

6174-613: The first isotope of lawrencium by irradiating californium (mostly californium-252 ) with boron-10 and boron-11 ions. The mass number of this isotope was not clearly established (possibly 258 or 259) at the time. In 1965, Lr was synthesized by Flyorov et al. from Am and O . Thus IUPAC recognized the nuclear physics teams at Dubna and Berkeley as the co-discoverers of lawrencium. Thirty-four isotopes of actinium and eight excited isomeric states of some of its nuclides are known, ranging in mass number from 203 to 236. Three isotopes, Ac , Ac and Ac , were found in nature and

6272-614: The first sample of uranium metal by heating uranium tetrachloride with metallic potassium . The atomic mass of uranium was then calculated as 120, but Dmitri Mendeleev in 1872 corrected it to 240 using his periodicity laws. This value was confirmed experimentally in 1882 by K. Zimmerman. Thorium oxide was discovered by Friedrich Wöhler in the mineral thorianite , which was found in Norway (1827). Jöns Jacob Berzelius characterized this material in more detail in 1828. By reduction of thorium tetrachloride with potassium, he isolated

6370-448: The fuel and dissolve it. Further, if correctly sited, any leakage will enter seawater, providing a safe dilution until decay. Geological stability against earthquakes and other extreme events can be further increased by careful site-selection. These safety factors multiply, extending the containment lifetime until most radioactive elements in the fuel have decayed, and only the longest-lived, least-radioactive isotopes remain. At this point,

6468-454: The gaining or losing of elemental ions such as a proton, H , in neutral molecules. For example, when ammonia , NH 3 , accepts a proton, H —a process called protonation —it forms the ammonium ion, NH + 4 . Ammonia and ammonium have the same number of electrons in essentially the same electronic configuration , but ammonium has an extra proton that gives it a net positive charge. Ammonia can also lose an electron to gain

6566-435: The gas through the application of an electric field. The Geiger–Müller tube and the proportional counter both use a phenomenon known as a Townsend avalanche to multiply the effect of the original ionizing event by means of a cascade effect whereby the free electrons are given sufficient energy by the electric field to release further electrons by ion impact. When writing the chemical formula for an ion, its net charge

6664-407: The given nuclides, alpha decay plays almost no role in the formation and decay of the actinides in a power reactor, as the residence time of the nuclear fuel in the reactor core is rather short (a few years). Exceptions are the two relatively short-lived nuclides Cm (T 1/2  = 163 d) and Pu (T 1/2  = 2.9 y). Only for these two cases, the α decay is marked on the nuclide map by

6762-399: The isotopes have short lifetimes, except for protactinium-231 (half-life 32,760 years). The most important isotopes are Pa and Pa , which is an intermediate product in obtaining uranium-233 and is the most affordable among artificial isotopes of protactinium. Pa has convenient half-life and energy of γ-radiation , and thus was used in most studies of protactinium chemistry. Protactinium-233

6860-650: The largest half-life of 4.51 × 10 years. The worldwide production of uranium in 2009 amounted to 50,572 tonnes , of which 27.3% was mined in Kazakhstan . Other important uranium mining countries are Canada (20.1%), Australia (15.7%), Namibia (9.1%), Russia (7.0%), and Niger (6.4%). The most abundant thorium minerals are thorianite ( ThO 2 ), thorite ( ThSiO 4 ) and monazite , ( (Th,Ca,Ce)PO 4 ). Most thorium minerals contain uranium and vice versa; and they all have significant fraction of lanthanides. Rich deposits of thorium minerals are located in

6958-440: The late actinides (from curium onwards) behave similarly to the lanthanides, the elements thorium , protactinium , and uranium are much more similar to transition metals in their chemistry, with neptunium , plutonium , and americium occupying an intermediate position. All actinides are radioactive and release energy upon radioactive decay; naturally occurring uranium and thorium, and synthetically produced plutonium are

7056-417: The least energy. For example, a sodium atom, Na, has a single electron in its valence shell, surrounding 2 stable, filled inner shells of 2 and 8 electrons. Since these filled shells are very stable, a sodium atom tends to lose its extra electron and attain this stable configuration, becoming a sodium cation in the process On the other hand, a chlorine atom, Cl, has 7 electrons in its valence shell, which

7154-641: The liquid or solid state when salts interact with solvents (for example, water) to produce solvated ions , which are more stable, for reasons involving a combination of energy and entropy changes as the ions move away from each other to interact with the liquid. These stabilized species are more commonly found in the environment at low temperatures. A common example is the ions present in seawater, which are derived from dissolved salts. As charged objects, ions are attracted to opposite electric charges (positive to negative, and vice versa) and repelled by like charges. When they move, their trajectories can be deflected by

7252-409: The lowest measured ionization energy of all the elements and helium has the greatest. In general, the ionization energy of metals is much lower than the ionization energy of nonmetals , which is why, in general, metals will lose electrons to form positively charged ions and nonmetals will gain electrons to form negatively charged ions. Ionic bonding is a kind of chemical bonding that arises from

7350-458: The luminescence of the Sun to the existence of the Earth's ionosphere . Atoms in their ionic state may have a different color from neutral atoms, and thus light absorption by metal ions gives the color of gemstones . In both inorganic and organic chemistry (including biochemistry), the interaction of water and ions is often relevant for understanding properties of systems; an example of their importance

7448-505: The metal and named it thorium after the Norse god of thunder and lightning Thor . The same isolation method was later used by Péligot for uranium. Actinium was discovered in 1899 by André-Louis Debierne , an assistant of Marie Curie , in the pitchblende waste left after removal of radium and polonium. He described the substance (in 1899) as similar to titanium and (in 1900) as similar to thorium. The discovery of actinium by Debierne

7546-424: The more systematic results on Pu are summarized in the table (no other plutonium isotopes could be detected in those samples). The upper limit of abundance of the longest-living isotope of plutonium, Pu, is 3 × 10 %. Plutonium could not be detected in samples of lunar soil. Owing to its scarcity in nature, most plutonium is produced synthetically. Negative ion An ion ( / ˈ aɪ . ɒ n , - ən / )

7644-743: The most abundant actinides on Earth. These have been used in nuclear reactors , and uranium and plutonium are critical elements of nuclear weapons . Uranium and thorium also have diverse current or historical uses, and americium is used in the ionization chambers of most modern smoke detectors . Of the actinides, primordial thorium and uranium occur naturally in substantial quantities. The radioactive decay of uranium produces transient amounts of actinium and protactinium, and atoms of neptunium and plutonium are occasionally produced from transmutation reactions in uranium ores . The other actinides are purely synthetic elements . Nuclear weapons tests have released at least six actinides heavier than plutonium into

7742-479: The most common Earth anion, oxygen . From this fact it is apparent that most of the space of a crystal is occupied by the anion and that the cations fit into the spaces between them." The terms anion and cation (for ions that respectively travel to the anode and cathode during electrolysis) were introduced by Michael Faraday in 1834 following his consultation with William Whewell . Ions are ubiquitous in nature and are responsible for diverse phenomena from

7840-402: The much longer-lived Pa. The name was shortened to protactinium in 1949. This element was little characterized until 1960, when Alfred Maddock and his co-workers in the U.K. isolated 130 grams of protactinium from 60 tonnes of waste left after extraction of uranium from its ore. Neptunium (named for the planet Neptune , the next planet out from Uranus, after which uranium was named)

7938-454: The mutual attraction of oppositely charged ions. Ions of like charge repel each other, and ions of opposite charge attract each other. Therefore, ions do not usually exist on their own, but will bind with ions of opposite charge to form a crystal lattice . The resulting compound is called an ionic compound , and is said to be held together by ionic bonding . In ionic compounds there arise characteristic distances between ion neighbours from which

8036-451: The nature of these species, but he knew that since metals dissolved into and entered a solution at one electrode and new metal came forth from a solution at the other electrode; that some kind of substance has moved through the solution in a current. This conveys matter from one place to the other. In correspondence with Faraday, Whewell also coined the words anode and cathode , as well as anion and cation as ions that are attracted to

8134-577: The others were produced in the laboratory; only the three natural isotopes are used in applications. Actinium-225 is a member of the radioactive neptunium series ; it was first discovered in 1947 as a decay product of uranium-233 and it is an α-emitter with a half-life of 10 days. Actinium-225 is less available than actinium-228, but is more promising in radiotracer applications. Actinium-227 (half-life 21.77 years) occurs in all uranium ores, but in small quantities. One gram of uranium (in radioactive equilibrium) contains only 2 × 10 gram of Ac. Actinium-228

8232-408: The phrase "actinide hypothesis" (the implication being that a "hypothesis" is something that has not been decisively proven) remained in active use by scientists through the late 1950s. At present, there are two major methods of producing isotopes of transplutonium elements: (1) irradiation of the lighter elements with neutrons ; (2) irradiation with accelerated charged particles. The first method

8330-635: The requisite equipment in the Onkalo tunnels will begin. The contract was awarded to Skanska , and the expected date of completion will be in summer 2022. The operation of the facility will begin in the 2020s. The Östhammar facility will have space for 6,000 capsules and the plan is to deposit 200 capsules into storage annually. In 2012, a research group at the Royal Institute of Technology in Stockholm, Sweden, published research that suggests that

8428-664: The respective electrodes. Svante Arrhenius put forth, in his 1884 dissertation, the explanation of the fact that solid crystalline salts dissociate into paired charged particles when dissolved, for which he would win the 1903 Nobel Prize in Chemistry. Arrhenius' explanation was that in forming a solution, the salt dissociates into Faraday's ions, he proposed that ions formed even in the absence of an electric current. Ions in their gas-like state are highly reactive and will rapidly interact with ions of opposite charge to give neutral molecules or ionic salts. Ions are also produced in

8526-539: The short-lived isotope Pa (half-life 1.17 minutes) during their studies of the U decay chain . They named the new element brevium (from Latin brevis meaning brief); the name was changed to protoactinium (from Greek πρῶτος + ἀκτίς meaning "first beam element") in 1918 when two groups of scientists, led by the Austrian Lise Meitner and Otto Hahn of Germany and Frederick Soddy and John Arnold Cranston of Great Britain, independently discovered

8624-414: The slow β-decay of the parent isotope Bk and a large cross section of interaction with neutrons, but it can be accumulated in the isotopically pure form as the β-decay product of (pre-selected) Bk. Californium produced by reactor-irradiation of plutonium mostly consists of Cf and Cf, the latter being predominant for large neutron fluences, and its study is hindered by the strong neutron radiation. Among

8722-434: The spatial extension and the ionic radius of individual ions may be derived. The most common type of ionic bonding is seen in compounds of metals and nonmetals (except noble gases , which rarely form chemical compounds). Metals are characterized by having a small number of electrons in excess of a stable, closed-shell electronic configuration . As such, they have the tendency to lose these extra electrons in order to attain

8820-455: The wrong conclusions were drawn. Actinides The actinide ( / ˈ æ k t ɪ n aɪ d / ) or actinoid ( / ˈ æ k t ɪ n ɔɪ d / ) series encompasses at least the 14 metallic chemical elements in the 5f series, with atomic numbers from 89 to 102, actinium through nobelium . (Number 103, lawrencium , is sometimes also included despite being part of the 6d transition series.) The actinide series derives its name from

8918-455: Was able to precipitate a yellow compound (likely sodium diuranate ) by dissolving pitchblende in nitric acid and neutralizing the solution with sodium hydroxide . He then reduced the obtained yellow powder with charcoal, and extracted a black substance that he mistook for metal. Sixty years later, the French scientist Eugène-Melchior Péligot identified it as uranium oxide. He also isolated

9016-542: Was attributed to spontaneous fission owing to the large speed of the products and to other decay channels, such as neutron emission and nuclear fission . Uranium and thorium were the first actinides discovered . Uranium was identified in 1789 by the German chemist Martin Heinrich Klaproth in pitchblende ore. He named it after the planet Uranus , which had been discovered eight years earlier. Klaproth

9114-702: Was discovered by Edwin McMillan and Philip H. Abelson in 1940 in Berkeley, California . They produced the Np isotope (half-life 2.4 days) by bombarding uranium with slow neutrons . It was the first transuranium element produced synthetically. Transuranium elements do not occur in sizeable quantities in nature and are commonly synthesized via nuclear reactions conducted with nuclear reactors. For example, under irradiation with reactor neutrons, uranium-238 partially converts to plutonium-239 : This synthesis reaction

9212-452: Was discovered not by its own radiation but by the radiation of the daughter products. Owing to the close similarity of actinium and lanthanum and low abundance, pure actinium could only be produced in 1950. The term actinide was probably introduced by Victor Goldschmidt in 1937. Protactinium was possibly isolated in 1900 by William Crookes . It was first identified in 1913, when Kasimir Fajans and Oswald Helmuth Göhring encountered

9310-472: Was however questioned in 1971 and 2000, arguing that Debierne's publications in 1904 contradicted his earlier work of 1899–1900. This view instead credits the 1902 work of Friedrich Oskar Giesel , who discovered a radioactive element named emanium that behaved similarly to lanthanum. The name actinium comes from the Ancient Greek : ακτίς, ακτίνος (aktis, aktinos) , meaning beam or ray. This metal

9408-419: Was named after the village of Ytterby in Sweden. In 1945, B. B. Cunningham obtained the first bulk chemical compound of a transplutonium element, namely americium hydroxide . Over the few years, milligram quantities of americium and microgram amounts of curium were accumulated that allowed production of isotopes of berkelium and californium. Sizeable amounts of these elements were produced in 1958, and

9506-872: Was suggested in 1934 by Enrico Fermi , based on his experiments. However, even though four actinides were known by that time, it was not yet understood that they formed a family similar to lanthanides. The prevailing view that dominated early research into transuranics was that they were regular elements in the 7th period, with thorium, protactinium and uranium corresponding to 6th-period hafnium , tantalum and tungsten , respectively. Synthesis of transuranics gradually undermined this point of view. By 1944, an observation that curium failed to exhibit oxidation states above 4 (whereas its supposed 6th period homolog, platinum , can reach oxidation state of 6) prompted Glenn Seaborg to formulate an " actinide hypothesis ". Studies of known actinides and discoveries of further transuranic elements provided more data in support of this position, but

9604-555: Was used by Fermi and his collaborators in their design of the reactors located at the Hanford Site , which produced significant amounts of plutonium-239 for the nuclear weapons of the Manhattan Project and the United States' post-war nuclear arsenal. Actinides with the highest mass numbers are synthesized by bombarding uranium, plutonium, curium and californium with ions of nitrogen, oxygen, carbon, neon or boron in

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