Nobelium is a
synthetic chemical element
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler sub ...
with the
symbol
A symbol is a mark, sign, or word that indicates, signifies, or is understood as representing an idea, object, or relationship. Symbols allow people to go beyond what is known or seen by creating linkages between otherwise very different conc ...
No and
atomic number
The atomic number or nuclear charge number (symbol ''Z'') of a chemical element is the charge number of an atomic nucleus. For ordinary nuclei, this is equal to the proton number (''n''p) or the number of protons found in the nucleus of every ...
102. It is named in honor of
Alfred Nobel
Alfred Bernhard Nobel ( , ; 21 October 1833 – 10 December 1896) was a Swedes, Swedish chemist, engineer, inventor, businessman, and Philanthropy, philanthropist. He is best known for having bequeathed his fortune to establish the Nobel ...
, the inventor of
dynamite
Dynamite is an explosive made of nitroglycerin, sorbents (such as powdered shells or clay), and Stabilizer (chemistry), stabilizers. It was invented by the Swedish people, Swedish chemist and engineer Alfred Nobel in Geesthacht, Northern Germa ...
and benefactor of science. A
radioactive
Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is consid ...
metal
A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...
, it is the tenth
transuranic element
The transuranium elements (also known as transuranic elements) are the chemical elements with atomic numbers greater than 92, which is the atomic number of uranium. All of these elements are unstable and decay radioactively into other elements. ...
and is the penultimate member of the
actinide series
The actinide () or actinoid () series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The inform ...
. Like all elements with atomic number over 100, nobelium can only be produced in
particle accelerator
A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams.
Large accelerators are used for fundamental research in particle ...
s by bombarding lighter elements with charged particles. A total of twelve
nobelium isotopes are known to exist; the most stable is
259No with a
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...
of 58 minutes, but the shorter-lived
255No (half-life 3.1 minutes) is most commonly used in chemistry because it can be produced on a larger scale.
Chemistry experiments have confirmed that nobelium behaves as a heavier
homolog
In biology, homology is similarity due to shared ancestry between a pair of structures or genes in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats and birds, the arms of prima ...
to
ytterbium
Ytterbium is a chemical element with the symbol Yb and atomic number 70. It is a metal, the fourteenth and penultimate element in the lanthanide series, which is the basis of the relative stability of its +2 oxidation state. However, like the othe ...
in the periodic table. The chemical properties of nobelium are not completely known: they are mostly only known in
aqueous solution
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be re ...
. Before nobelium's discovery, it was predicted that it would show a stable +2
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
as well as the +3 state characteristic of the other actinides; these predictions were later confirmed, as the +2 state is much more stable than the +3 state in
aqueous solution
An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be re ...
and it is difficult to keep nobelium in the +3 state.
In the 1950s and 1960s, many claims of the discovery of nobelium were made from laboratories in
Sweden
Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...
, the
Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
, and the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
. Although the Swedish scientists soon retracted their claims, the priority of the discovery and therefore the
naming of the element was disputed between Soviet and American scientists, and it was not until 1997 that the
International Union of Pure and Applied Chemistry
The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
(IUPAC) credited the Soviet team with the discovery, but retained nobelium, the Swedish proposal, as the name of the element due to its long-standing use in the literature.
Introduction
Discovery
![AlfredNobel2](https://upload.wikimedia.org/wikipedia/commons/d/d2/AlfredNobel2.jpg)
The discovery of element 102 was a complicated process and was claimed by groups from
Sweden
Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic country located on ...
, the
United States
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
, and the
Soviet Union
The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen national ...
. The first complete and incontrovertible report of its
detection {{Unreferenced, date=March 2018
In general, detection is the action of accessing information without specific cooperation from with the sender.
In the history of radio communications, the term " detector" was first used for a device that detected ...
only came in 1966 from the
Joint Institute of Nuclear Research at
Dubna
Dubna ( rus, Дубна́, p=dʊbˈna) is a town in Moscow Oblast, Russia. It has a status of ''naukograd'' (i.e. town of science), being home to the Joint Institute for Nuclear Research, an international nuclear physics research center and one o ...
(then in the Soviet Union).
[ (Note: for Part I see Pure and Applied Chemistry, vol. 63, no. 6, pp. 879–886, 1991)]
The first announcement of the discovery of element 102 was announced by physicists at the
Nobel Institute
The Norwegian Nobel Institute ( no, Det Norske Nobelinstitutt) is located in Oslo, Norway. The institute is located at Henrik Ibsen Street 51 in the center of the city. It is situated just by the side of the Royal Palace.
History
The institute ...
in Sweden in 1957. The team reported that they had bombarded a
curium
Curium is a transuranic, radioactive chemical element with the symbol Cm and atomic number 96. This actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first inte ...
target with
carbon-13
Carbon-13 (13C) is a natural, stable isotope of carbon with a nucleus containing six protons and seven neutrons. As one of the environmental isotopes, it makes up about 1.1% of all natural carbon on Earth.
Detection by mass spectrometry
A mass ...
ions for twenty-five hours in half-hour intervals. Between bombardments,
ion-exchange chemistry was performed on the target. Twelve out of the fifty bombardments contained samples emitting (8.5 ± 0.1)
MeV
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacu ...
alpha particle
Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produce ...
s, which were in drops which eluted earlier than
fermium
Fermium is a synthetic element with the symbol Fm and atomic number 100. It is an actinide and the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic qua ...
(atomic number ''Z'' = 100) and
californium
Californium is a radioactive chemical element with the symbol Cf and atomic number 98. The element was first synthesized in 1950 at Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory), by bombarding ...
(''Z'' = 98). The
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...
reported was 10 minutes and was assigned to either
251102 or
253102, although the possibility that the alpha particles observed were from a presumably short-lived
mendelevium
Mendelevium is a synthetic element with the symbol Md ( formerly Mv) and atomic number 101. A metallic radioactive transuranium element in the actinide series, it is the first element by atomic number that currently cannot be produced in macroscopi ...
(''Z'' = 101) isotope created from the electron capture of element 102 was not excluded.
The team proposed the name ''nobelium'' (No) for the new element,
which was immediately approved by IUPAC,
a decision which the Dubna group characterized in 1968 as being hasty.
In 1958, scientists at the
Lawrence Berkeley National Laboratory
Lawrence Berkeley National Laboratory (LBNL), commonly referred to as the Berkeley Lab, is a United States Department of Energy National Labs, United States national laboratory that is owned by, and conducts scientific research on behalf of, t ...
repeated the experiment. The Berkeley team, consisting of
Albert Ghiorso
Albert Ghiorso (July 15, 1915 – December 26, 2010) was an American nuclear scientist and co-discoverer of a record 12 chemical elements on the periodic table. His research career spanned six decades, from the early 1940s to the late 1990s.
Biog ...
,
Glenn T. Seaborg
Glenn Theodore Seaborg (; April 19, 1912February 25, 1999) was an American chemist whose involvement in the synthesis, discovery and investigation of ten transuranium elements earned him a share of the 1951 Nobel Prize in Chemistry. His work i ...
,
John R. Walton and
Torbjørn Sikkeland, used the new heavy-
ion
An ion () 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 conve ...
linear accelerator
A linear particle accelerator (often shortened to linac) is a type of particle accelerator that accelerates charged subatomic particles or ions to a high speed by subjecting them to a series of oscillating electric potentials along a linear ...
(HILAC) to bombard a curium target (95%
244Cm and 5%
246Cm) with
13C and
12C ions. They were unable to confirm the 8.5 MeV activity claimed by the Swedes but were instead able to detect decays from fermium-250, supposedly the daughter of
254102 (produced from the curium-246), which had an apparent
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...
of ~3 s.
In 1959, the Swedish team attempted to explain the Berkeley team's inability to detect element 102 in 1958, maintaining that they did discover it. However, later work has shown that no nobelium isotopes lighter than
259No (no heavier isotopes could have been produced in the Swedish experiments) with a half-life over 3 minutes exist, and that the Swedish team's results are most likely from
thorium
Thorium is a weakly radioactive metallic chemical element with the symbol Th and atomic number 90. Thorium is silvery and tarnishes black when it is exposed to air, forming thorium dioxide; it is moderately soft and malleable and has a high me ...
-225, which has a half-life of 8 minutes and quickly undergoes triple alpha decay to
polonium
Polonium is a chemical element with the symbol Po and atomic number 84. Polonium is a chalcogen. A rare and highly radioactive metal with no stable isotopes, polonium is chemically similar to selenium and tellurium, though its metallic character ...
-213, which has a decay energy of 8.53612 MeV. This hypothesis is lent weight by the fact that thorium-225 can easily be produced in the reaction used and would not be separated out by the chemical methods used. Later work on nobelium also showed that the divalent state is more stable than the trivalent one and hence that the samples emitting the alpha particles could not have contained nobelium, as the divalent nobelium would not have eluted with the other trivalent actinides.
Thus, the Swedish team later retracted their claim and associated the activity to background effects.
Later 1963 Dubna work confirmed that
254102 could be produced in this reaction, but that its half-life was actually . In 1967, the Berkeley team attempted to defend their work, stating that the isotope found was indeed
250Fm but the isotope that the half-life measurements actually related to was californium-244,
granddaughter
Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Ideal ...
of
252102, produced from the more abundant curium-244. Energy differences were then attributed to "resolution and drift problems", although these had not been previously reported and should also have influenced other results. 1977 experiments showed that
252102 indeed had a 2.3-second half-life. However, 1973 work also showed that the
250Fm recoil could have also easily been produced from the
isomeric transition
A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited states have ha ...
of
250mFm (half-life 1.8 s) which could also have been formed in the reaction at the energy used.
Given this, it is probable that no nobelium was actually produced in this experiment.
In 1959, the team continued their studies and claimed that they were able to produce an isotope that decayed predominantly by emission of an 8.3 MeV alpha particle, with a
half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable ato ...
of 3 s with an associated 30%
spontaneous fission
Spontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements. The nuclear binding energy of the elements reaches its maximum at an atomic mass number of about 56 (e.g., iron-56); spontaneous breakdo ...
branch. The activity was initially assigned to
254102 but later changed to
252102. However, they also noted that it was not certain that nobelium had been produced due to difficult conditions.
The Berkeley team decided to adopt the proposed name of the Swedish team, "nobelium", for the element.
: + → → + 4
Meanwhile, in Dubna, experiments were carried out in 1958 and 1960 aiming to synthesize element 102 as well. The first 1958 experiment bombarded
plutonium-239
Plutonium-239 (239Pu or Pu-239) is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 is also used for that purpose. Plutonium-239 is also one of the three main ...
and
-241 with
oxygen-16
Oxygen-16 (16O) is a stable isotope of oxygen, having 8 neutrons and 8 protons in its nucleus. It has a mass of . Oxygen-16 is the most abundant isotope of oxygen and accounts for 99.762% of oxygen's natural abundance. The relative and absolute ...
ions. Some alpha decays with energies just over 8.5 MeV were observed, and they were assigned to
251,252,253102, although the team wrote that formation of isotopes from
lead
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...
or
bismuth
Bismuth is a chemical element with the Symbol (chemistry), symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental ...
impurities (which would not produce nobelium) could not be ruled out. While later 1958 experiments noted that new isotopes could be produced from
mercury
Mercury commonly refers to:
* Mercury (planet), the nearest planet to the Sun
* Mercury (element), a metallic chemical element with the symbol Hg
* Mercury (mythology), a Roman god
Mercury or The Mercury may also refer to:
Companies
* Merc ...
,
thallium
Thallium is a chemical element with the Symbol (chemistry), symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists W ...
, lead, or bismuth impurities, the scientists still stood by their conclusion that element 102 could be produced from this reaction, mentioning a half-life of under 30 seconds and a decay energy of (8.8 ± 0.5) MeV. Later 1960 experiments proved that these were background effects. 1967 experiments also lowered the decay energy to (8.6 ± 0.4) MeV, but both values are too high to possibly match those of
253No or
254No.
The Dubna team later stated in 1970 and again in 1987 that these results were not conclusive.
In 1961, Berkeley scientists claimed the discovery of
element 103 in the reaction of californium with
boron
Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...
and carbon ions. They claimed the production of the isotope
257103, and also claimed to have synthesized an alpha decaying isotope of element 102 that had a half-life of 15 s and alpha decay energy 8.2 MeV. They assigned this to
255102 without giving a reason for the assignment. The values do not agree with those now known for
255No, although they do agree with those now known for
257No, and while this isotope probably played a part in this experiment, its discovery was inconclusive.
Work on element 102 also continued in Dubna, and in 1964, experiments were carried out there to detect alpha-decay daughters of element 102 isotopes by synthesizing element 102 from the reaction of a
uranium-238
Uranium-238 (238U or U-238) is the most common isotope of uranium found in nature, with a relative abundance of 99%. Unlike uranium-235, it is non-fissile, which means it cannot sustain a chain reaction in a thermal-neutron reactor. However, it ...
target with
neon
Neon is a chemical element with the symbol Ne and atomic number 10. It is a noble gas. Neon is a colorless, odorless, inert monatomic gas under standard conditions, with about two-thirds the density of air. It was discovered (along with krypton ...
ions. The products were carried along a
silver
Silver is a chemical element with the Symbol (chemistry), symbol Ag (from the Latin ', derived from the Proto-Indo-European wikt:Reconstruction:Proto-Indo-European/h₂erǵ-, ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, whi ...
catcher foil and purified chemically, and the isotopes
250Fm and
252Fm were detected. The yield of
252Fm was interpreted as evidence that its parent
256102 was also synthesized: as it was noted that
252Fm could also be produced directly in this reaction by the simultaneous emission of an alpha particle with the excess neutrons, steps were taken to ensure that
252Fm could not go directly to the catcher foil. The half-life detected for
256102 was 8 s, which is much higher than the more modern 1967 value of (3.2 ± 0.2) s.
Further experiments were conducted in 1966 for
254102, using the reactions
243 Am(
15 N,4n)
254102 and
238U(
22Ne,6n)
254102, finding a half-life of (50 ± 10) s: at that time the discrepancy between this value and the earlier Berkeley value was not understood, although later work proved that the formation of the isomer
250mFm was less likely in the Dubna experiments than at the Berkeley ones. In hindsight, the Dubna results on
254102 were probably correct and can be now considered a conclusive detection of element 102.
One more very convincing experiment from Dubna was published in 1966, again using the same two reactions, which concluded that
254102 indeed had a half-life much longer than the 3 seconds claimed by Berkeley.
Later work in 1967 at Berkeley and 1971 at the
Oak Ridge National Laboratory
Oak Ridge National Laboratory (ORNL) is a U.S. multiprogram science and technology national laboratory sponsored by the U.S. Department of Energy (DOE) and administered, managed, and operated by UT–Battelle as a federally funded research and ...
fully confirmed the discovery of element 102 and clarified earlier observations.
In December 1966, the Berkeley group repeated the Dubna experiments and fully confirmed them, and used this data to finally assign correctly the isotopes they had previously synthesized but could not yet identify at the time, and thus claimed to have discovered nobelium in 1958 to 1961.
: + → → + 6
In 1969, the Dubna team carried out chemical experiments on element 102 and concluded that it behaved as the heavier homologue of
ytterbium
Ytterbium is a chemical element with the symbol Yb and atomic number 70. It is a metal, the fourteenth and penultimate element in the lanthanide series, which is the basis of the relative stability of its +2 oxidation state. However, like the othe ...
. The Russian scientists proposed the name ''joliotium'' (Jo) for the new element after
Irène Joliot-Curie
Irène Joliot-Curie (; ; 12 September 1897 – 17 March 1956) was a French chemist, physicist and politician, the elder daughter of Pierre and Marie Curie, and the wife of Frédéric Joliot-Curie. Jointly with her husband, Joliot-Curie was award ...
, who had recently died, creating an
element naming controversy
The currently accepted names and symbols of the chemical elements are determined by the International Union of Pure and Applied Chemistry (IUPAC), usually following recommendations by the recognized discoverers of each element. However the names o ...
that would not be resolved for several decades, which each group using its own proposed names.
In 1992, the
IUPAC
The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is ...
-
IUPAP
The International Union of Pure and Applied Physics (IUPAP ) is an international non-governmental organization whose mission is to assist in the worldwide development of physics, to foster international cooperation in physics, and to help in the ...
Transfermium Working Group (TWG) reassessed the claims of discovery and concluded that only the Dubna work from 1966 correctly detected and assigned decays to nuclei with atomic number 102 at the time. The Dubna team are therefore officially recognised as the discoverers of nobelium although it is possible that it was detected at Berkeley in 1959.
This decision was criticized by Berkeley the following year, calling the reopening of the cases of elements 101 to 103 a "futile waste of time", while Dubna agreed with IUPAC's decision.
In 1994, as part of an attempted resolution to the element naming controversy, IUPAC ratified names for elements 101–109. For element 102, it ratified the name ''nobelium'' (No) on the basis that it had become entrenched in the literature over the course of 30 years and that
Alfred Nobel
Alfred Bernhard Nobel ( , ; 21 October 1833 – 10 December 1896) was a Swedes, Swedish chemist, engineer, inventor, businessman, and Philanthropy, philanthropist. He is best known for having bequeathed his fortune to establish the Nobel ...
should be commemorated in this fashion.
Because of outcry over the 1994 names, which mostly did not respect the choices of the discoverers, a comment period ensued, and in 1995 IUPAC named element 102 ''flerovium'' (Fl) as part of a new proposal, after either
Georgy Flyorov
Georgii Nikolayevich Flyorov (also spelled Flerov, rus, Гео́ргий Никола́евич Флёров, p=gʲɪˈorgʲɪj nʲɪkɐˈlajɪvʲɪtɕ ˈflʲɵrəf; 2 March 1913 – 19 November 1990) was a Soviet physicist who is known for h ...
or his eponymous
Flerov Laboratory of Nuclear Reactions
The Joint Institute for Nuclear Research (JINR, russian: Объединённый институт ядерных исследований, ОИЯИ), in Dubna, Moscow Oblast (110 km north of Moscow), Russia, is an international research ce ...
.
This proposal was also not accepted, and in 1997 the name ''nobelium'' was restored.
Today the name ''flerovium'', with the same symbol, refers to
element 114
Flerovium is a Transactinide element, superheavy chemical element with Chemical symbol, symbol Fl and atomic number 114. It is an extremely radioactive synthetic element. It is named after the Flerov Laboratory of Nuclear Reactions of the Joint ...
.
Characteristics
Physical
![Fblock fd promotion energy](https://upload.wikimedia.org/wikipedia/commons/7/70/Fblock_fd_promotion_energy.png)
In the
periodic table
The periodic table, also known as the periodic table of the (chemical) elements, is a rows and columns arrangement of the chemical elements. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of ch ...
, nobelium is located to the right of the actinide
mendelevium
Mendelevium is a synthetic element with the symbol Md ( formerly Mv) and atomic number 101. A metallic radioactive transuranium element in the actinide series, it is the first element by atomic number that currently cannot be produced in macroscopi ...
, to the left of the actinide
lawrencium
Lawrencium is a synthetic chemical element with the symbol Lr (formerly Lw) and atomic number 103. It is named in honor of Ernest Lawrence, inventor of the cyclotron, a device that was used to discover many artificial radioactive elements. A radi ...
, and below the lanthanide
ytterbium
Ytterbium is a chemical element with the symbol Yb and atomic number 70. It is a metal, the fourteenth and penultimate element in the lanthanide series, which is the basis of the relative stability of its +2 oxidation state. However, like the othe ...
. Nobelium metal has not yet been prepared in bulk quantities, and bulk preparation is currently impossible.
Nevertheless, a number of predictions and some preliminary experimental results have been done regarding its properties.
The lanthanides and actinides, in the metallic state, can exist as either divalent (such as
europium
Europium is a chemical element with the symbol Eu and atomic number 63. Europium is the most reactive lanthanide by far, having to be stored under an inert fluid to protect it from atmospheric oxygen or moisture. Europium is also the softest lanth ...
and
ytterbium
Ytterbium is a chemical element with the symbol Yb and atomic number 70. It is a metal, the fourteenth and penultimate element in the lanthanide series, which is the basis of the relative stability of its +2 oxidation state. However, like the othe ...
) or trivalent (most other lanthanides) metals. The former have f
''n''s
2 configurations, whereas the latter have f
''n''−1d
1s
2 configurations. In 1975, Johansson and Rosengren examined the measured and predicted values for the
cohesive energies (
enthalpies of crystallization) of the metallic
lanthanide
The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and yttr ...
s and
actinide
The actinide () or actinoid () series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The inform ...
s, both as divalent and trivalent metals.
The conclusion was that the increased binding energy of the
nf
136d
17s
2 configuration over the
nf
147s
2 configuration for nobelium was not enough to compensate for the energy needed to promote one 5f electron to 6d, as is true also for the very late actinides: thus
einsteinium
Einsteinium is a synthetic element with the symbol Es and atomic number 99. Einsteinium is a member of the actinide series and it is the seventh transuranium element. It was named in honor of Albert Einstein.
Einsteinium was discovered as a com ...
,
fermium
Fermium is a synthetic element with the symbol Fm and atomic number 100. It is an actinide and the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic qua ...
,
mendelevium
Mendelevium is a synthetic element with the symbol Md ( formerly Mv) and atomic number 101. A metallic radioactive transuranium element in the actinide series, it is the first element by atomic number that currently cannot be produced in macroscopi ...
, and nobelium were expected to be divalent metals, although for nobelium this prediction has not yet been confirmed.
The increasing predominance of the divalent state well before the actinide series concludes is attributed to the
relativistic stabilization of the 5f electrons, which increases with increasing atomic number: an effect of this is that nobelium is predominantly divalent instead of trivalent, unlike all the other lanthanides and actinides. In 1986, nobelium metal was estimated to have an
enthalpy of sublimation
In thermodynamics, the enthalpy of sublimation, or heat of sublimation, is the heat required to sublimate (change from solid to gas) one mole of a substance at a given combination of temperature and pressure, usually standard temperature and p ...
between 126 kJ/mol, a value close to the values for einsteinium, fermium, and mendelevium and supporting the theory that nobelium would form a divalent metal.
Like the other divalent late actinides (except the once again trivalent lawrencium), metallic nobelium should assume a
face-centered cubic
In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in crystals and minerals.
There are three main varieties of ...
crystal structure.
Divalent nobelium metal should have a
metallic radius
Metallic bonding is a type of chemical bonding that arises from the electrostatic attractive force between conduction electrons (in the form of an electron cloud of delocalized electrons) and positively charged metal ions. It may be descr ...
of around 197
pm.
Nobelium's melting point has been predicted to be 827 °C, the same value as that estimated for the neighboring element mendelevium. Its density is predicted to be around 9.9 ± 0.4 g/cm
3.
Chemical
The chemistry of nobelium is incompletely characterized and is known only in aqueous solution, in which it can take on the +3 or +2
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
s, the latter being more stable.
It was largely expected before the discovery of nobelium that in solution, it would behave like the other actinides, with the trivalent state being predominant; however, Seaborg predicted in 1949 that the +2 state would also be relatively stable for nobelium, as the No
2+ ion would have the ground-state electron configuration
nf
14, including the stable filled 5f
14 shell. It took nineteen years before this prediction was confirmed.
In 1967, experiments were conducted to compare nobelium's chemical behavior to that of
terbium
Terbium is a chemical element with the symbol Tb and atomic number 65. It is a silvery-white, rare earth metal that is malleable, and ductile. The ninth member of the lanthanide series, terbium is a fairly electropositive metal that reacts with wa ...
,
californium
Californium is a radioactive chemical element with the symbol Cf and atomic number 98. The element was first synthesized in 1950 at Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory), by bombarding ...
, and
fermium
Fermium is a synthetic element with the symbol Fm and atomic number 100. It is an actinide and the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic qua ...
. All four elements were reacted with
chlorine
Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...
and the resulting chlorides were deposited along a tube, along which they were carried by a gas. It was found that the nobelium chloride produced was strongly
adsorbed
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a ...
on solid surfaces, proving that it was not very
volatile, like the chlorides of the other three investigated elements. However, both NoCl
2 and NoCl
3 were expected to exhibit nonvolatile behavior and hence this experiment was inconclusive as to what the preferred oxidation state of nobelium was.
Determination of nobelium's favoring of the +2 state had to wait until the next year, when
cation-exchange chromatography and
coprecipitation
In chemistry, coprecipitation (CPT) or co-precipitation is the carrying down by a precipitate of substances normally soluble under the conditions employed. Analogously, in medicine, coprecipitation is specifically the precipitation of an unbound " ...
experiments were carried out on around fifty thousand
255No atoms, finding that it behaved differently from the other actinides and more like the divalent
alkaline earth metal
The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).. The elements have very similar properties: they are al ...
s. This proved that in aqueous solution, nobelium is most stable in the divalent state when strong
oxidizers are absent.
Later experimentation in 1974 showed that nobelium eluted with the alkaline earth metals, between
Ca2+ and
Sr2+.
Nobelium is the only known f-block element for which the +2 state is the most common and stable one in aqueous solution. This occurs because of the large energy gap between the 5f and 6d orbitals at the end of the actinide series.
It is expected that the relativistic stabilization of the 7s subshell greatly destabilizes nobelium dihydride, NoH
2, and relativistic stabilisation of the 7p
1/2 spinor over the 6d
3/2 spinor mean that excited states in nobelium atoms have 7s and 7p contribution instead of the expected 6d contribution. The long No–H distances in the NoH
2 molecule and the significant charge transfer lead to extreme ionicity with a
dipole moment of 5.94
D for this molecule. In this molecule, nobelium is expected to exhibit
main-group-like behavior, specifically acting like an
alkaline earth metal
The alkaline earth metals are six chemical elements in group 2 of the periodic table. They are beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).. The elements have very similar properties: they are al ...
with its ''n''s
2 valence shell configuration and core-like 5f orbitals.
Nobelium's
complexing ability with
chloride
The chloride ion is the anion (negatively charged ion) Cl−. It is formed when the element chlorine (a halogen) gains an electron or when a compound such as hydrogen chloride is dissolved in water or other polar solvents. Chloride salts ...
ions is most similar to that of
barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element.
Th ...
, which complexes rather weakly.
Its complexing ability with
citrate
Citric acid is an organic compound with the chemical formula HOC(CO2H)(CH2CO2H)2. It is a colorless weak organic acid. It occurs naturally in citrus fruits. In biochemistry, it is an intermediate in the citric acid cycle, which occurs in t ...
,
oxalate
Oxalate (IUPAC: ethanedioate) is an anion with the formula C2O42−. This dianion is colorless. It occurs naturally, including in some foods. It forms a variety of salts, for example sodium oxalate (Na2C2O4), and several esters such as dimethyl o ...
, and
acetate
An acetate is a salt (chemistry), salt formed by the combination of acetic acid with a base (e.g. Alkali metal, alkaline, Alkaline earth metal, earthy, Transition metal, metallic, nonmetallic or radical Radical (chemistry), base). "Acetate" als ...
in an aqueous solution of 0.5 M
ammonium nitrate
Ammonium nitrate is a chemical compound with the chemical formula . It is a white crystalline salt consisting of ions of ammonium and nitrate. It is highly soluble in water and hygroscopic as a solid, although it does not form hydrates. It is ...
is between that of calcium and strontium, although it is somewhat closer to that of strontium.
The
standard reduction potential
Redox potential (also known as oxidation / reduction potential, ''ORP'', ''pe'', ''E_'', or E_) is a measure of the tendency of a chemical species to acquire electrons from or lose electrons to an electrode and thereby be reduced or oxidised respe ...
of the ''E''°(No
3+→No
2+) couple was estimated in 1967 to be between +1.4 and +1.5
V;
it was later found in 2009 to be only about +0.75 V. The positive value shows that No
2+ is more stable than No
3+ and that No
3+ is a good oxidizing agent. While the quoted values for the ''E''°(No
2+→No
0) and ''E''°(No
3+→No
0) vary among sources, the accepted standard estimates are −2.61 and −1.26 V.
It has been predicted that the value for the ''E''°(No
4+→No
3+) couple would be +6.5 V.
The
Gibbs energies of formation for No
3+ and No
2+ are estimated to be −342 and −480
kJ/mol, respectively.
Atomic
A nobelium atom has 102 electrons. They are expected to be arranged in the configuration
nf
147s
2 (ground state
term symbol In quantum mechanics
Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including ...
1S
0), although experimental verification of this electron configuration had not yet been made as of 2006. The sixteen electrons in the 5f and 7s subshells are
valence electron
In chemistry and physics, a valence electron is an electron in the outer shell associated with an atom, and that can participate in the formation of a chemical bond if the outer shell is not closed. In a single covalent bond, a shared pair forms ...
s.
In forming compounds, three valence electrons may be lost, leaving behind a
nf
13 core: this conforms to the trend set by the other actinides with their
nf
''n'' electron configurations in the tripositive state. Nevertheless, it is more likely that only two valence electrons may be lost, leaving behind a stable
nf
14 core with a filled 5f
14 shell. The first
ionization potential
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule i ...
of nobelium was measured to be at most (6.65 ± 0.07)
eV in 1974, based on the assumption that the 7s electrons would ionize before the 5f ones;
this value has not yet been refined further due to nobelium's scarcity and high radioactivity.
[Lide, David R. (editor), ''CRC Handbook of Chemistry and Physics, 84th Edition'', CRC Press, Boca Raton (FL), 2003, section 10, ''Atomic, Molecular, and Optical Physics; Ionization Potentials of Atoms and Atomic Ions''] The ionic radius of
hexacoordinate
In chemistry, crystallography, and materials science, the coordination number, also called ligancy, of a central atom in a molecule or crystal is the number of atoms, molecules or ions bonded to it. The ion/molecule/atom surrounding the central ...
and octacoordinate No
3+ had been preliminarily estimated in 1978 to be around 90 and 102 pm respectively;
the ionic radius of No
2+ has been experimentally found to be 100 pm to two
significant figure
Significant figures (also known as the significant digits, ''precision'' or ''resolution'') of a number in positional notation are digits in the number that are reliable and necessary to indicate the quantity of something.
If a number expre ...
s.
The
enthalpy of hydration of No
2+ has been calculated as 1486 kJ/mol.
Isotopes
Thirteen isotopes of nobelium are known, with
mass number
The mass number (symbol ''A'', from the German word ''Atomgewicht'' tomic weight, also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It is approxima ...
s 249–260 and 262; all are radioactive.
Additionally,
nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy excited state, higher energy levels than in the ground state of the same nucleus. "Metastable" describes nuclei whose excited ...
s are known for mass numbers 250, 251, 253, and 254.
Of these, the longest-lived isotope is
259No with a half-life of 58 minutes, and the longest-lived isomer is
251mNo with a half-life of 1.7 seconds.
However, the still undiscovered isotope
261No is predicted to have a still longer half-life of 170 min.
Additionally, the shorter-lived
255No (half-life 3.1 minutes) is more often used in chemical experimentation because it can be produced in larger quantities from irradiation of
californium-249 with
carbon-12
Carbon-12 (12C) is the most abundant of the two stable isotopes of carbon (carbon-13 being the other), amounting to 98.93% of element carbon on Earth; its abundance is due to the triple-alpha process by which it is created in stars. Carbon-12 i ...
ions.
After
259No and
255No, the next most stable nobelium isotopes are
253No (half-life 1.62 minutes),
254No (51
second
The second (symbol: s) is the unit of time in the International System of Units (SI), historically defined as of a day – this factor derived from the division of the day first into 24 hours, then to 60 minutes and finally to 60 seconds ...
s),
257No (25 seconds),
256No (2.91 seconds), and
252No (2.57 seconds).
All of the remaining nobelium isotopes have half-lives that are less than a second, and the shortest-lived known nobelium isotope (
250No) has a half-life of only 0.25
millisecond
A millisecond (from '' milli-'' and second; symbol: ms) is a unit of time in the International System of Units (SI) equal to one thousandth (0.001 or 10−3 or 1/1000) of a second and to 1000 microseconds.
A unit of 10 milliseconds may be called ...
s.
The isotope
254No is especially interesting theoretically as it is in the middle of a series of
prolate
A spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadric surface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A spheroid has circ ...
nuclei from
231 Pa to
279 Rg, and the formation of its nuclear isomers (of which two are known) is controlled by
proton orbitals such as 2f
5/2 which come just above the spherical proton shell; it can be synthesized in the reaction of
208Pb with
48Ca.
The half-lives of nobelium isotopes increase smoothly from
250No to
253No. However, a dip appears at
254No, and beyond this the half-lives of
even-even nobelium isotopes drop sharply as
spontaneous fission
Spontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements. The nuclear binding energy of the elements reaches its maximum at an atomic mass number of about 56 (e.g., iron-56); spontaneous breakdo ...
becomes the dominant decay mode. For example, the half-life of
256No is almost three seconds, but that of
258No is only 1.2 milliseconds.
This shows that at nobelium, the mutual repulsion of protons poses a limit to the
region of long-lived nuclei in the
actinide
The actinide () or actinoid () series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The inform ...
series.
The even-odd nobelium isotopes mostly continue to have longer half-lives as their mass numbers increase, with a dip in the trend at
257No.
Preparation and purification
The isotopes of nobelium are mostly produced by bombarding actinide targets (
uranium
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
,
plutonium
Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibi ...
,
curium
Curium is a transuranic, radioactive chemical element with the symbol Cm and atomic number 96. This actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first inte ...
,
californium
Californium is a radioactive chemical element with the symbol Cf and atomic number 98. The element was first synthesized in 1950 at Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory), by bombarding ...
, or
einsteinium
Einsteinium is a synthetic element with the symbol Es and atomic number 99. Einsteinium is a member of the actinide series and it is the seventh transuranium element. It was named in honor of Albert Einstein.
Einsteinium was discovered as a com ...
), with the exception of nobelium-262, which is produced as the
daughter
A daughter is a female offspring; a girl or a woman in relation to her parents. Daughterhood is the state of being someone's daughter. The male counterpart is a son. Analogously the name is used in several areas to show relations between group ...
of lawrencium-262.
The most commonly used isotope,
255No, can be produced from bombarding
curium
Curium is a transuranic, radioactive chemical element with the symbol Cm and atomic number 96. This actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first inte ...
-248 or californium-249 with carbon-12: the latter method is more common. Irradiating a 350
μg cm
−2 target of californium-249 with three trillion (3 × 10
12) 73
MeV
In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy gained by a single electron accelerating from rest through an electric potential difference of one volt in vacu ...
carbon-12 ions per second for ten minutes can produce around 1200 nobelium-255 atoms.
Once the nobelium-255 is produced, it can be separated out similarly as used to purify the neighboring actinide mendelevium. The recoil
momentum
In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
of the produced nobelium-255 atoms is used to bring them physically far away from the target from which they are produced, bringing them onto a thin foil of metal (usually
beryllium
Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to form mi ...
,
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. I ...
,
platinum
Platinum is a chemical element with the symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name originates from Spanish , a diminutive of "silver".
Platinu ...
, or
gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...
) just behind the target in a vacuum: this is usually combined by trapping the nobelium atoms in a gas atmosphere (frequently
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...
), and carrying them along with a gas jet from a small opening in the reaction chamber. Using a long
capillary tube
Capillary action (sometimes called capillarity, capillary motion, capillary rise, capillary effect, or wicking) is the process of a liquid flowing in a narrow space without the assistance of, or even in opposition to, any external forces li ...
, and including
potassium chloride
Potassium chloride (KCl, or potassium salt) is a metal halide salt composed of potassium and chlorine. It is odorless and has a white or colorless vitreous crystal appearance. The solid dissolves readily in water, and its solutions have a salt ...
aerosols in the helium gas, the nobelium atoms can be transported over tens of
meter
The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its prefi ...
s.
The thin layer of nobelium collected on the foil can then be removed with dilute acid without completely dissolving the foil.
The nobelium can then be isolated by exploiting its tendency to form the divalent state, unlike the other trivalent actinides: under typically used
elution
In analytical and organic chemistry, elution is the process of extracting one material from another by washing with a solvent; as in washing of loaded ion-exchange resins to remove captured ions.
In a liquid chromatography experiment, for exam ...
conditions (
bis-(2-ethylhexyl) phosphoric acid (HDEHP) as stationary organic phase and 0.05 M
hydrochloric acid
Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid
Acid strength is the tendency of an acid, symbol ...
as mobile aqueous phase, or using 3 M hydrochloric acid as an eluant from
cation-exchange
Ion exchange is a reversible interchange of one kind of ion present in an insoluble solid with another of like charge present in a solution surrounding the solid with the reaction being used especially for softening or making water demineralised, ...
resin columns), nobelium will pass through the column and elute while the other trivalent actinides remain on the column.
However, if a direct "catcher" gold foil is used, the process is complicated by the need to separate out the gold using
anion-exchange
Ion exchange is a reversible interchange of one kind of ion present in an insoluble solid with another of like charge present in a solution surrounding the solid with the reaction being used especially for softening or making water demineralised, ...
chromatography
In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system (a ...
before isolating the nobelium by elution from
chromatographic
In chemical analysis, chromatography is a laboratory technique for the separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it through a system (a ...
extraction columns using HDEHP.
Notes
References
Bibliography
*
*
*
*
*
External links
Chart of Nuclides. nndc.bnl.gov
Los Alamos National Laboratory – Nobeliumat ''
The Periodic Table of Videos
''Periodic Videos'' (also known as ''The Periodic Table of Videos'') is a video project and YouTube channel on chemistry. It consists of a series of videos about chemical elements and the periodic table, with additional videos on other topics i ...
'' (University of Nottingham)
{{Good article
Chemical elements
Chemical elements with face-centered cubic structure
Actinides
Synthetic elements
Alfred Nobel