Instruct: Given a question, retrieve documents that answer the question.
Query: What is the heaviest lanthanide?
All of the lanthanides form LnQ (Q= S, Se, Te). The sesquisulfides can be produced by reaction of the elements or (with the exception of EuS) sulfidizing the oxide (LnO) with HS. The sesquisulfides, LnS generally lose sulfur when heated and can form a range of compositions between LnS and LnS. The sesquisulfides are insulators but some of the LnS are metallic conductors (e.g. CeS) formulated (Ln) (S) (e), while others (e.g. EuS and SmS) are semiconductors. Structurally the sesquisulfides adopt structures that vary according to the size of the Ln metal. The lighter and larger lanthanides favoring 7-coordinate metal atoms, the heaviest and smallest lanthanides (Yb and Lu) favoring 6 coordination and the rest structures with a mixture of 6 and 7 coordination. Polymorphism is common amongst the sesquisulfides. The colors of the sesquisulfides vary metal to metal and depend on the polymorphic form. The colors of the γ-sesquisulfides are LaS, white/yellow; CeS, dark red; PrS, green; NdS, light green; GdS, sand; TbS, light yellow and DyS, orange. The shade of γ-CeS can be varied by doping with Na or Ca with hues ranging from dark red to yellow, and CeS based pigments are used commercially and are seen as low toxicity substitutes for cadmium based pigments.
Ununennium, also known as eka-francium or simply element 119, is the hypothetical chemical element with symbol Uue and atomic number 119. "Ununennium" and "Uue" are the temporary systematic IUPAC name and symbol respectively, until a permanent name is decided upon. In the periodic table of the elements, it is expected to be an s-block element, an alkali metal, and the first element in the eighth period. It is the lightest element that has not yet been synthesized.
Osmium (from Greek ὀσμή "osme", "smell") is a chemical element with symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mostly in platinum ores. Osmium is the densest naturally occurring element, with an experimentally measured (using x-ray crystallography) density of . Manufacturers use its alloys with platinum, iridium, and other platinum-group metals to make fountain pen nib tipping, electrical contacts, and in other applications that require extreme durability and hardness. The element's abundance in the Earth's crust is among the rarest.
Hassium (Hs) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was Hs in 1984. There are 12 known isotopes from Hs to Hs and 1–4 isomers. The longest-lived isotope is Hs with a half-life of 10 seconds.Super-heavy elements such as hassium are produced by bombarding lighter elements in particle accelerators that induce fusion reactions. Whereas most of the isotopes of hassium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher atomic numbers.
Density criteria range from above 3.5 g/cm to above 7 g/cm. Atomic weight definitions can range from greater than sodium (atomic weight 22.98); greater than 40 (excluding s- and f-block metals, hence starting with scandium); or more than 200, i.e. from mercury onwards. Atomic numbers of heavy metals are generally given as greater than 20 (calcium); sometimes this is capped at 92 (uranium). Definitions based on atomic number have been criticised for including metals with low densities. For example, rubidium in group (column) 1 of the periodic table has an atomic number of 37 but a density of only 1.532 g/cm, which is below the threshold figure used by other authors. The same problem may occur with atomic weight based definitions.
A 2007 calculation on the decay properties of unknown neutron-rich isotopes of superheavy elements suggested that the isotope Hs may be the most stable superheavy nucleus against alpha decay and spontaneous fission, as a consequence of the shell closure at "N" = 184. As such, it was considered as a candidate to exist in nature. However, this nucleus is predicted to be highly unstable toward beta decay, and any beta-stable isotopes of hassium (such as Hs) would be too unstable in the other decay channels to possibly be observed in nature. Indeed, a subsequent search for Hs in nature along with its congener osmium was unsuccessful, setting an upper limit to its abundance at 3×10 grams of hassium per gram of osmium.
Hahn's death did not stop his public acclamation. Proposals were made at different times, first in 1971 by American chemists, that the newly synthesized element no. 105 should be named hahnium in Hahn's honor; in 1997 the IUPAC (International Union of Pure and Applied Chemistry) named it dubnium, after the Russian research center in Dubna (see element naming controversy). Although element 108 was given the name hassium (after Hesse) by its officially recognized German discoverers in 1992, a 1994 IUPAC committee recommended that it be named hahnium (Hn), in spite of the long-standing convention to give the discoverer the right to suggest a name. This recommendation was not adopted, following protests from the German discoverers, and the name hassium (Hs) was adopted internationally in 1997.
Hassium is a synthetic chemical element with symbol Hs and atomic number 108. It is named after the German state of Hesse. It is a synthetic element and radioactive; the most stable known isotope, Hs, has a half-life of approximately 10 seconds.
Iridium is one of the nine least abundant stable elements in Earth's crust, having an average mass fraction of 0.001 ppm in crustal rock; platinum is 10 times more abundant, gold is 40 times more abundant, and silver and mercury are 80 times more abundant. Tellurium is about as abundant as iridium. In contrast to its low abundance in crustal rock, iridium is relatively common in meteorites, with concentrations of 0.5 ppm or more. The overall concentration of iridium on Earth is thought to be much higher than what is observed in crustal rocks, but because of the density and siderophilic ("iron-loving") character of iridium, it descended below the crust and into Earth's core when the planet was still molten.
In the Earth's crust, thorium is much more abundant: with an abundance of 8.1 parts per million (ppm), it is one of the most abundant of the heavy elements, almost as abundant as lead (13 ppm) and more abundant than tin (2.1 ppm). This is because thorium is likely to form oxide minerals that do not sink into the core; it is classified as a lithophile. Common thorium compounds are also poorly soluble in water. Thus, even though the Earth contains the same abundances of the elements as the Solar System as a whole, there is more accessible thorium than heavy platinum group metals in the crust.
The actual mass of an atom at rest is often expressed using the unified atomic mass unit (u), also called dalton (Da). This unit is defined as a twelfth of the mass of a free neutral atom of carbon-12, which is approximately . Hydrogen-1 (the lightest isotope of hydrogen which is also the nuclide with the lowest mass) has an atomic weight of 1.007825 u. The value of this number is called the atomic mass. A given atom has an atomic mass approximately equal (within 1%) to its mass number times the atomic mass unit (for example the mass of a nitrogen-14 is roughly 14 u). However, this number will not be exactly an integer except in the case of carbon-12 (see below). The heaviest stable atom is lead-208, with a mass of .
Lanthanum barium copper oxide, or LBCO, was discovered in 1986 and was the first high temperature superconductor. Johannes Georg Bednorz and K. Alex Müller shared the 1987 Nobel Prize in physics for its discovery.
Palladium is a chemical element with the chemical symbol Pd and an atomic number of 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired by her when she slew Pallas. Palladium, platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). These have similar chemical properties, but palladium has the lowest melting point and is the least dense of them.
The name "hassium" was proposed by Peter Armbruster and his colleagues, the officially recognised German discoverers, in September 1992. It is derived from the Latin name "Hassia" for the German state of Hesse where the institute is located. In 1994, IUPAC Commission on Nomenclature of Inorganic Chemistry recommended that element 108 be named "hahnium" (Hn) after the German physicist Otto Hahn so that elements named after Hahn and Lise Meitner (meitnerium) would be next to each other, honoring their joint discovery of nuclear fission. This was because they felt that Hesse did not merit an element being named after it. GSI protested saying that this contradicted the long-standing convention to give the discoverer the right to suggest a name; the American Chemical Society supported the GSI. IUPAC relented and the name "hassium" (Hs) was adopted internationally in 1997.
Hassium has no stable or naturally occurring isotopes. Several radioactive isotopes have been synthesized in the laboratory, either by fusing two atoms or by observing the decay of heavier elements. Twelve different isotopes have been reported with atomic masses from 263 to 277 (with the exceptions of 272, 274, and 276), three of which, hassium-265, hassium-267, hassium-269, have known metastable states. Most of these decay predominantly through alpha decay, but some also undergo spontaneous fission.
The Bornean orangutan is the third-heaviest living primate after the two species of gorilla, and the largest truly arboreal (or tree-dwelling) animal alive today. Body weights broadly overlap with the considerably taller "Homo sapiens", but the latter is considerably more variable in size. By comparison, the Sumatran orangutan is similar in size but, on average, is marginally lighter in weight. A survey of wild orangutans found that males weigh on average , ranging from , and long; females average , ranging from , and long. While in captivity, orangutans can grow considerably overweight, up to more than . The heaviest known male orangutan in captivity was an obese male named "Andy", who weighed in 1959 when he was 13 years old.
Californium is a radioactive chemical element with symbol Cf and atomic number 98. The element was first synthesized in 1950 at the Lawrence Berkeley National Laboratory (then the University of California Radiation Laboratory), by bombarding curium with alpha particles (helium-4 ions). 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 the university and the state of California.
The heaviest beetle, indeed the heaviest insect stage, is the larva of the goliath beetle, "Goliathus goliatus", which can attain a mass of at least and a length of . Adult male goliath beetles are the heaviest beetle in its adult stage, weighing and measuring up to . Adult elephant beetles, "Megasoma elephas" and "Megasoma actaeon" often reach and .
One mole of a substance always contains almost exactly the "standard atomic weight" or "molar mass" of that substance; however, this may or may not be true for the "atomic mass," depending on whether or not the element exists naturally in more than one isotope. For example, the standard atomic weight of iron is 55.847 g/mol, and therefore one mole of iron as commonly found on earth has a mass of 55.847 grams. The "atomic mass" of the Fe isotope is 55.935 u and one mole of Fe atoms would then in theory have a mass of 55.935 g, but such amounts of pure Fe have never been found (or separated out) on Earth. However, there are 22 mononuclidic elements of which essentially only a single isotope is found in nature (common examples are fluorine, sodium, aluminum and phosphorus) and for these elements the standard atomic weight and atomic mass are the same. Samples of these elements therefore may serve as reference standards for certain atomic mass values.
The alkali metals are a group (column) in the periodic table consisting of the chemical elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). This group lies in the s-block of the periodic table of elements as all alkali metals have their outermost electron in an s-orbital: this shared electron configuration results in their having very similar characteristic properties. Indeed, the alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterised homologous behaviour.
Platinum is a member of the platinum group of elements and group 10 of the periodic table of elements. It has six naturally occurring isotopes. It is one of the rarer elements in Earth's crust, with an average abundance of approximately 5 μg/kg. It occurs in some nickel and copper ores along with some native deposits, mostly in South Africa, which accounts for 80% of the world production. Because of its scarcity in Earth's crust, only a few hundred tonnes are produced annually, and given its important uses, it is highly valuable and is a major precious metal commodity.
Hexaborides, LnB have been reported for all of the lanthanides. They all have the CaB structure, containing B clusters. They are non-stoichiometric due to cation defects. The hexaborides of the lighter lanthanides (La – Sm) melt without decomposition, EuB decomposes to boron and metal and the heavier lanthanides decompose to LnB with exception of YbB which decomposes forming YbB. The stability has in part been correlated to differences in volatility between the lanthanide metals. In EuB and YbB the metals have an oxidation state of +2 whereas in the rest of the lanthanide hexaborides it is +3. This rationalises the differences in conductivity, the extra electrons in the Ln hexaborides entering conduction bands. EuB is a semiconductor and the rest are good conductors. LaB and CeB are thermionic emitters, used, for example, in scanning electron microscopes.
Lanthanide-carbon σ bonds are well known; however as the 4f electrons have a low probability of existing at the outer region of the atom there is little effective orbital overlap, resulting in bonds with significant ionic character. As such organo-lanthanide compounds exhibit carbanion-like behavior, unlike the behavior in transition metal organometallic compounds. Because of their large size, lanthanides tend to form more stable organometallic derivatives with bulky ligands to give compounds such as Ln[CH(SiMe)]. Analogues of uranocene are derived from dilithiocyclooctatetraene, LiCH. Organic lanthanide(II) compounds are also known, such as Cp*Eu.
The lanthanide contraction is responsible for the great geochemical divide that splits the lanthanides into light and heavy-lanthanide enriched minerals, the latter being almost inevitably associated with and dominated by yttrium. This divide is reflected in the first two "rare earths" that were discovered: yttria (1794) and ceria (1803). The geochemical divide has put more of the light lanthanides in the Earth's crust, but more of the heavy members in the Earth's mantle. The result is that although large rich ore-bodies are found that are enriched in the light lanthanides, correspondingly large ore-bodies for the heavy members are few. The principal ores are monazite and bastnäsite. Monazite sands usually contain all the lanthanide elements, but the heavier elements are lacking in bastnäsite. The lanthanides obey the Oddo-Harkins rule – odd-numbered elements are less abundant than their even-numbered neighbors.
The only tetrahalides known are the tetrafluorides of cerium, praseodymium, terbium, neodymium and dysprosium, the last two known only under matrix isolation conditions.
All of the lanthanides form trihalides with fluorine, chlorine, bromine and iodine. They are all high melting and predominantly ionic in nature. The fluorides are only slightly soluble in water and are not sensitive to air, and this contrasts with the other halides which are air sensitive, readily soluble in water and react at high temperature to form oxohalides.
The trihalides were important as pure metal can be prepared from them. In the gas phase the trihalides are planar or approximately planar, the lighter lanthanides have a lower % of dimers, the heavier lanthanides a higher proportion. The dimers have a similar structure to AlCl.