Lawrencium

General properties
Name, symbol, number	lawrencium, Lr, 103
Element category	actinide
Group, period, block	n/a, 7, f
Standard atomic weight	(262)
Electron configuration	[Rn] 7s2 5f14 7p1 2, 8, 18, 32, 32, 8, 3
History
Discovery	Lawrence Berkeley National Laboratory (1961)

Lawrencium is a radioactive synthetic chemical element with the symbol Lr (formerly Lw) and atomic number 103. In the periodic table of the elements, it is a period 7 d-block element and the last element of the actinide series. Chemistry experiments have confirmed that lawrencium behaves as the heavier homologue to lutetium and is chemically similar to other actinides.

Lawrencium was first synthesized by the nuclear-physics team led by Albert Ghiorso on February 14, 1961, at the Lawrence Berkeley National Laboratory of the University of California. The first atoms of lawrencium were produced by bombarding a three-milligram target consisting of three isotopes of the element californium with boron-10 and boron-11 nuclei from the Heavy Ion Linear Accelerator. The team suggested the name lawrencium, and the symbol "Lw", but IUPAC changed the symbol to "Lr" in 1963. It was the last element of the actinide series to be produced.

All isotopes of lawrencium are radioactive; its most stable known isotope is lawrencium-262, with a half-life of approximately 3.6 hours. All its isotopes except for lawrencium-260, -261 and -262 decay with a half-life of less than a minute.

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Nobelium

General properties
Name, symbol, number	nobelium, No, 102
Element category	actinide
Group, period, block	n/a, 7, f
Standard atomic weight	(259)
Electron configuration	[Rn] 5f14 7s2 2, 8, 18, 32, 31, 8, 2
History
Discovery	Joint Institute for Nuclear Research (1966)

Nobelium is a synthetic element with the symbol No and atomic number 102. It was first correctly identified in 1966 by scientists at the Flerov Laboratory of Nuclear Reactions in Dubna, Soviet Union. Little is known about the element but limited chemical experiments have shown that it forms a stable divalent ion in solution as well as the predicted trivalent ion that is associated with its presence as one of the actinides.

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Mendelevium

General properties
Name, symbol, number	mendelevium, Md, 101
Element category	actinide
Group, period, block	n/a, 7, f
Standard atomic weight	(258)
Electron configuration	[Rn] 5f13 7s2 2, 8, 18, 32, 31, 8, 2
History
Discovery	Lawrence Berkeley National Laboratory (1955)

Mendelevium is a synthetic element with the symbol Md(formerly Mv) and the atomic number 101. A metallic radioactive transuranic element in the actinide series, mendelevium is usually synthesized by bombarding einsteinium with alpha particles. It was named after Dmitri Ivanovich Mendeleev, who created the Periodic Table. Mendeleev's periodic system is the fundamental way to classify all the chemical elements. The name "mendelevium" was accepted by the International Union of Pure and Applied Chemistry (IUPAC). On the other hand, the proposed symbol "Mv" submitted by the discoverers was not accepted, and IUPAC changed the symbol to "Md" in 1963.

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Fermium

General properties
Name, symbol, number	fermium, Fm, 100
Element category	actinide
Group, period, block	n/a, 7, f
Standard atomic weight	(257)
Electron configuration	[Rn] 5f12 7s2 2, 8, 18, 32, 30, 8, 2
History
Discovery	Lawrence Berkeley National Laboratory (1952)

Fermium is a synthetic element with symbol Fm and atomic number 100. It is a member of the actinide series. It is the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic quantities, although pure fermium metal has not yet been prepared. A total of 19 isotopes are known, with ²⁵⁷Fm being the longest-lived one with a half-life of 100.5 days.

It was discovered in the debris of the first hydrogen bomb explosion in 1952, and named after Nobel laureate Enrico Fermi, one of the pioneers of nuclear physics. Its chemistry is typical of the late actinides, with a preponderance of the +3 oxidation state but also an accessible +2 oxidation state. Owing to the small amounts of produced fermium and its short half-life, there are currently no uses for it outside of basic scientific research. Like all synthetic elements, isotopes of fermium are extremely radioactive and are considered highly toxic.

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Einsteinium

General properties
Name, symbol, number	einsteinium, Es, 99
Element category	actinide
Group, period, block	n/a, 7, f
Standard atomic weight	(252)
Electron configuration	[Rn] 5f11 7s2 2, 8, 18, 32, 29, 8, 2
History
Discovery	Lawrence Berkeley National Laboratory (1952)

Einsteinium is a synthetic element with the symbol Es and atomic number 99. It is the seventh transuranic element, and an actinide.

Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952, and named after Albert Einstein. Its most common isotope einsteinium-253 (half life 20.47 days) is produced artificially from decay of californium-253 in a few dedicated high-power nuclear reactors with a total yield on the order of one milligram per year. The reactor synthesis is followed by a complex procedure of separating einsteinium-253 from other actinides and products of their decay. Other isotopes are synthesized in various laboratories, but at much smaller amounts, by bombarding heavy actinide elements with light ions. Owing to the small amounts of produced einsteinium and the short half-life of its most easily produced isotope, there are currently almost no practical applications for it outside of basic scientific research. In particular, einsteinium was used to synthesize, for the first time, 17 atoms of the new element mendelevium in 1955.

Einsteinium is a soft, silvery, paramagnetic metal. Its chemistry is typical of the late actinides, with a preponderance of the +3 oxidation state; the +2 oxidation state is also accessible, especially in solids. The high radioactivity of einsteinium-253 produces a visible glow and rapidly damages its crystalline metal lattice, with released heat of about 1000 watts per gram. Difficulty in studying its properties is due to einsteinium-253's conversion to berkelium and then californium at a rate of about 3% per day. The isotope of einsteinium with the longest half life, einsteinium-252 (half life 471.7 days) would be more suitable for investigation of physical properties, but it has proven far more difficult to produce and is available only in minute quantities, and not in bulk. Einsteinium is the element with the highest atomic number which has been observed in macroscopic quantities in its pure form, and this was the common short-lived isotope einsteinium-253.

Like all synthetic transuranic elements, isotopes of einsteinium are extremely radioactive and are considered highly dangerous to health on ingestion.

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Californium

General properties
Name, symbol, number	californium, Cf, 98
Element category	actinide
Group, period, block	n/a, 7, f
Standard atomic weight	(251)
Electron configuration	[Rn] 5f10 7s2 2, 8, 18, 32, 28, 8, 2
History
Discovery	Lawrence Berkeley National Laboratory (1950)

Californium is a radioactive metallic chemical element with the symbol Cf and atomic number 98. The element was first made at the University of California, Berkeley in 1950 by bombarding curium with alpha particles (helium-4ions). It is an actinide element, the sixth transuranium element to be synthesized, and has the second-highest atomic mass of all the elements that have been produced in amounts large enough to see with the unaided eye (after einsteinium). The element was named after California and the University of California. It is the heaviest element to occur naturally on Earth; heavier elements can only be produced by synthesis.

Two crystalline forms exist for californium under normal pressure: one above 900 °C and one below 900 °C. A third form exists at high pressure. Californium slowly tarnishes in air at room temperature. Compounds of californium are dominated by a chemical form of the element, designated californium(III), that can participate in three chemical bonds. The most stable of californium's twenty known isotopes is californium-251, which has a half-life of 898 years. This short half-life means the element is not found in significant quantities in the Earth's crust. Californium-252, with a half-life of about 2.64 years, is the most common isotope used and is produced at the Oak Ridge National Laboratory in the United States and the Research Institute of Atomic Reactors in Russia.

Californium is one of the few transuranium elements that have practical applications. Most of these applications exploit the property of certain isotopes of californium to emit neutrons. For example, californium can be used to help start up nuclear reactors, and it is employed as a source of neutrons when studying materials with neutron diffraction and neutron spectroscopy. Californium can also be used in nuclear synthesis of higher mass elements; ununoctium (element 118) was synthesized by bombarding californium-249 atoms withcalcium-48 ions. Use of californium must take into account radiological concerns and the element's ability to disrupt the formation of red blood cells by bioaccumulating in skeletal tissue.

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Berkelium

General properties
Name, symbol, number	berkelium, Bk, 97
Element category	actinide
Group, period, block	n/a, 7, f
Standard atomic weight	(247)
Electron configuration	[Rn] 5f9 7s2 2, 8, 18, 32, 27, 8, 2
History
Discovery	Lawrence Berkeley National Laboratory (1949)

Berkelium is a transuranic radioactive chemical element with the symbol Bk and atomic number 97, a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the University of California Radiation Laboratory where it was discovered in December 1949. This was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.

The major isotope of berkelium, berkelium-249, is synthesized in minute quantities in dedicated high-flux nuclear reactors, mainly at the Oak Ridge National Laboratory in Tennessee, USA, and at the Research Institute of Atomic Reactors in Dimitrovgrad, Russia. The production of the second-important isotope berkelium-247 involves the irradiation of the rare isotope curium-244 with high-energy alpha particles.

Just over one gram of berkelium has been produced in the United States since 1967. There is no practical application of berkelium outside of scientific research which is mostly directed at the synthesis of heavier transuranic elements and transactinides. A 22 milligram batch of berkelium-249 was prepared during a 250-day irradiation period and then purified for a further 90 days at Oak Ridge in 2009. This sample was used to synthesize the element ununseptium for the first time in 2009 at the Joint Institute for Nuclear Research, Russia, after it was bombarded withcalcium-48 ions for 150 days. This was a culmination of the Russia–US collaboration on the synthesis of elements 113 to 118.

Berkelium is a soft, silvery-white, radioactive metal. The berkelium-249 isotope emits low-energy electrons and thus is relatively safe to handle. However, it decays with a half-life of 330 days to californium-249, which is a strong and hazardous emitter of alpha particles. This gradual transformation is an important consideration when studying the properties of elemental berkelium and its chemical compounds, since the formation of californium brings not only chemical contamination, but also self-radiation damage, and self-heating from the emitted alpha particles.

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