Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom. The term isotope is formed from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table. It was coined by a Scottish doctor and writer Margaret Todd in 1913 in a suggestion to chemist Frederick Soddy.
Introduction
Isotope
Isotope | Introduction
Sorry. I cannot find the answer based on the context. The common allotrope of elemental oxygen on Earth is called dioxygen The common allotrope of elemental oxygen on Earth is called dioxygen. The common allotrope of elemental oxygen on Earth is called dioxygen.
oxygen (o2) is formed in photosynthesis as a direct result of
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Light-driven splitting of water during oxygenic photosynthesis
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how does lavoisier contribute?
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He conducted the first adequate quantitative experiments on oxidation and gave the first correct explanation of how combustion works
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what are its isotopes?
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They are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number
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what are its allotropes?
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Allotropy or allotropism () is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements. Allotropes are different structural modifications of an element; the atoms of the element are bonded together in a different manner. For example, the allotropes of carbon include diamond (the carbon atoms are bonded together in a tetrahedral lattice arrangement), graphite (the carbon atoms are bonded together in sheets of a hexagonal lattice), graphene (single sheets of graphite), and fullerenes (the carbon atoms are bonded together in spherical, tubular, or ellipsoidal formations).
Allotropy | Introduction
Allotropes of iron
Hexaferrum | See also
In that sense, allotropes are all homonuclear. Many elements have multiple allotropic forms. In addition to the most common form of gaseous oxygen, O, and ozone, there are other allotropes of oxygen. Sulfur forms several allotropes containing different numbers of sulfur atoms, including diatomic, triatomic, hexatomic and octatomic (S, S, S, S) forms, though the first three are rare. The element carbon is known to have a number of homonuclear molecules, including diamond and graphite.
Homonuclear molecule | Introduction
Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons but different numbers of neutrons in each atom. The term isotope is formed from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table. It was coined by a Scottish doctor and writer Margaret Todd in 1913 in a suggestion to chemist Frederick Soddy.
Isotope | Introduction
Isotopes are any of the several different forms of an element each having different atomic mass (mass number). Isotope can also refer to:
Isotope (disambiguation) | Introduction
β-rhombohedral boron has a unit cell containing 105–108 atoms. Most atoms form B discrete icosahedra; a few form partially interpenetrating icosahedra, and there are two deltahedral B units, and a single central B atom. For a long time, it was unclear whether the α or β phase is most stable at ambient conditions; however, gradually a consensus was reached that the β phase is the most thermodynamically stable allotrope.
Allotropes of boron | β-rhombohedral boron
Atoms of chemically pure elements may bond to each other chemically in more than one way, allowing the pure element to exist in multiple chemical structures (spatial arrangements of atoms), known as allotropes, which differ in their properties. For example, carbon can be found as diamond, which has a tetrahedral structure around each carbon atom; graphite, which has layers of carbon atoms with a hexagonal structure stacked on top of each other; graphene, which is a single layer of graphite that is very strong; fullerenes, which have nearly spherical shapes; and carbon nanotubes, which are tubes with a hexagonal structure (even these may differ from each other in electrical properties).
Chemical element | Allotropes
An alternate stable form, if it exists, may appear at pressures of at least 50 GPa and temperatures of at least 1,500 K; it has been thought to have an orthorhombic or a double hcp structure. as of December 2011, recent and ongoing experiments are being conducted on high-pressure and Superdense carbon allotropes.
Allotropes of iron | Experimental high temperature and pressure
The δ form has more typical metallic character, and is roughly as strong and malleable as aluminium. In fission weapons, the explosive shock waves used to compress a plutonium core will also cause a transition from the usual δ phase plutonium to the denser α form, significantly helping to achieve supercriticality. The ε phase, the highest temperature solid allotrope, exhibits anomalously high atomic self-diffusion compared to other elements.
Plutonium | Allotropes
The outer core surrounding the solid inner core is believed to be composed of liquid iron mixed with nickel and trace amounts of lighter elements.
Allotropes of iron | Introduction
Plutonium occurs in a variety of allotropes, even at ambient pressure. These allotropes differ widely in crystal structure and density; the α and δ allotropes differ in density by more than 25% at constant pressure.
Allotropes of plutonium | Introduction
Neutrons do not affect the electron configuration, but the sum of atomic number and the number of neutrons, or neutron number, is the mass of the nucleus. Atoms of a chemical element that differ only in neutron number are called isotopes. For example, carbon, with atomic number 6, has an abundant isotope carbon-12 with 6 neutrons and a rare isotope carbon-13 with 7 neutrons. Some elements occur in nature with only one stable isotope, such as fluorine. Other elements occur with many stable isotopes, such as tin with ten stable isotopes. The properties of an atomic nucleus are dependent on both atomic and neutron numbers.
Neutron | Introduction
All atoms of a given element are not necessarily identical, however. The number of neutrons may vary to form different isotopes, and energy levels may differ, resulting in different nuclear isomers. For example, there are two stable isotopes of chlorine: with 35 − 17 = 18 neutrons and with 37 − 17 = 20 neutrons.
Proton | Atomic number
Typically, elements capable of variable coordination number and/or oxidation states tend to exhibit greater numbers of allotropic forms. Another contributing factor is the ability of an element to catenate. Examples of allotropes include:
Allotropy | List of allotropes
Isotope masses from: Isotopic compositions and standard atomic masses from: Half-life, spin, and isomer data selected from:
Isotopes of iron | References
Cyclo[18]carbon (C) was synthesised in 2019.
Allotropes of carbon | Cyclocarbons
The latter synthesizes the lightest, most neutron-poor, isotopes of the elements heavier than iron from preexisting heavier isotopes.
Supernova nucleosynthesis | Introduction
Graphenylene is a single layer carbon material with biphenylene-like subunits as basis in its hexagonal lattice structure. It is also known as biphenylene-carbon.
Allotropes of carbon | Graphenylene
Although many other chemists have repeated this advice, IUPAC and most chemistry texts still favour the usage of allotrope and allotropy for elements only.
Allotropy | History
They subsequently explained why the minor Mo and Mo isotopes of the element molybdenum had become dominant in supernovae stardust explaining an experimental riddle in stardust isotopic abundances.
Donald D. Clayton | Nuclear physics origin of the chemical elements (<a href="Nucleosynthesis">Nucleosynthesis</a>)
The number of protons within the atom's nucleus is called atomic number and is equal to the number of electrons in the neutral (non-ionized) atom. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons. The number of nucleons (both protons and neutrons) in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number.
Isotope | Introduction
These stable even-proton odd-neutron nuclides tend to be uncommon by abundance in nature, generally because, to form and enter into primordial abundance, they must have escaped capturing neutrons to form yet other stable even-even isotopes, during both the s-process and r-process of neutron capture, during nucleosynthesis in stars. For this reason, only and are the most naturally abundant isotopes of their element.
Isotope | Even atomic number
Sullenger "et al." (1969) and McConville "et al." (1976) reported a cubic allotrope of boron, obtained in argon plasma experiments, with a unit cell of 1705±3 atoms and a density of 2.367 g/cm. While this allotrope is occasionally mentioned in the literature, no subsequent work appears to have been published either confirming or discrediting its existence. Donohue (1982) commented that the number of atoms in the unit cell did not appear to be icosahedrally related (the icosahedron being a motif common to boron structures).
Allotropes of boron | Cubic boron
A one-dimensional carbon polymer with the structure —(C≡C)—.
Allotropes of carbon | Linear acetylenic carbon
Isotopes were then explained as elements with the same number of protons, but different numbers of neutrons within the nucleus.
Atom | Discovery of the neutron
[[Category:Isotopes| ]] [[Category:Nuclear physics]]
Nuclide | External links
The discovery of the quasispherical allotropic molecule borospherene (B) was announced in July 2014.
Allotropes of boron | Borospherene
There are several known allotropes of oxygen. The most familiar is molecular oxygen (O), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (O). Others are:
Allotropes of oxygen | Introduction
The many radioisotopes that are not found in nature have been characterized after being artificially made. Certain elements have no stable isotopes and are composed "only" of radioactive isotopes: specifically the elements without any stable isotopes are technetium (atomic number 43), promethium (atomic number 61), and all observed elements with atomic numbers greater than 82.
Chemical element | Isotopes
Isotopes are atoms of the same element (that is, with the same number of protons in their atomic nucleus), but having "different" numbers of neutrons. Thus, for example, there are three main isotopes of carbon. All carbon atoms have 6 protons in the nucleus, but they can have either 6, 7, or 8 neutrons. Since the mass numbers of these are 12, 13 and 14 respectively, the three isotopes of carbon are known as carbon-12, carbon-13, and carbon-14, often abbreviated to C, C, and C. Carbon in everyday life and in chemistry is a mixture of C (about 98.9%), C (about 1.1%) and about 1 atom per trillion of C.
Chemical element | Isotopes
A neutral atom has the same number of electrons as protons. Thus different isotopes of a given element all have the same number of electrons and share a similar electronic structure. Because the chemical behavior of an atom is largely determined by its electronic structure, different isotopes exhibit nearly identical chemical behavior. The main exception to this is the kinetic isotope effect: due to their larger masses, heavier isotopes tend to react somewhat more slowly than lighter isotopes of the same element. This is most pronounced by far for protium (), deuterium (), and tritium (), because deuterium has twice the mass of protium and tritium has three times the mass of protium.
Isotope | Chemical and molecular properties
Atomic carbon is a very short-lived species and, therefore, carbon is stabilized in various multi-atomic structures with diverse molecular configurations called allotropes. The three relatively well-known allotropes of carbon are amorphous carbon, graphite, and diamond. Once considered exotic, fullerenes are nowadays commonly synthesized and used in research; they include buckyballs, carbon nanotubes, carbon nanobuds and nanofibers. Several other exotic allotropes have also been discovered, such as lonsdaleite, glassy carbon, carbon nanofoam and linear acetylenic carbon (carbyne). Graphene is a two-dimensional sheet of carbon with the atoms arranged in a hexagonal lattice. As of 2009, graphene appears to be the strongest material ever tested.
Carbon | Allotropes
The ability of an element to exist in one of many structural forms is known as 'allotropy'. The standard state, also known as the reference state, of an element is defined as its thermodynamically most stable state at a pressure of 1 bar and a given temperature (typically at 298.15 K). In thermochemistry, an element is defined to have an enthalpy of formation of zero in its standard state. For example, the reference state for carbon is graphite, because the structure of graphite is more stable than that of the other allotropes.
Chemical element | Allotropes
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Table of nuclides (segmented, narrow) | Isotopes for elements 0-14
Carbon is capable of forming many allotropes (structurally different forms of the same element) due to its valency. Well-known forms of carbon include diamond and graphite. In recent decades, many more allotropes have been discovered and researched including ball shapes such as buckminsterfullerene and sheets such as graphene. Larger scale structures of carbon include nanotubes, nanobuds and nanoribbons. Other unusual forms of carbon exist at very high temperatures or extreme pressures. Around 500 hypothetical 3-periodic allotropes of carbon are known at the present time, according to the Samara Carbon Allotrope Database (SACADA).
Allotropes of carbon | Introduction
Isotope masses from: Isotopic compositions and standard atomic masses from: Half-life, spin, and isomer data selected from:
Isotopes of hassium | References
For all elements, each individual isotope (nuclide) of mass number "A" was eventually found to have a mass very close to "A" times the mass of a hydrogen atom, with an error always less than 1%. This is a near miss to Prout's law being correct. Nevertheless, the rule was not found to predict isotope masses better than this for all isotopes, due mostly to mass-defects resulting from release of binding energy in atomic nuclei, when they are formed.
Prout's hypothesis | Influence
AA'-graphite is an allotrope of carbon similar to graphite, but where the layers are positioned differently to each other as compared to the order in graphite.
Allotropes of carbon | AA'-graphite
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Table of nuclides (segmented, wide) | Isotopes for elements 0-29
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Table of nuclides (segmented, narrow) | Isotopes for elements 15-29
Under certain conditions, carbon can be found in its atomic form. It is formed by passing large electric currents through carbon under very low pressures. It is extremely unstable, but it is an intermittent product used in the creation of carbenes. Diatomic carbon can also be found under certain conditions. It is often detected via spectroscopy in extraterrestrial bodies, including comets and certain stars.
Allotropes of carbon | Atomic and diatomic carbon
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Table of nuclides (segmented, narrow) | Isotopes for elements 45-59
Some of these structures were recognized as Schwarzites and they proposed a route to their synthesis.
Allotropes of carbon | Schwarzites
The number of neutrons in a nucleus usually has very little effect on an element's chemical properties (except in the case of hydrogen and deuterium). Thus, all carbon isotopes have nearly identical chemical properties because they all have six protons and six electrons, even though carbon atoms may, for example, have 6 or 8 neutrons. That is why the atomic number, rather than mass number or atomic weight, is considered the identifying characteristic of a chemical element. The symbol for atomic number is "Z".
Chemical element | Atomic number
The dimeric unit contains a triple bond and is analogous to N. It can also be generated as a transient intermediate in solution by thermolysis of organophosphorus precursor reagents. At still higher temperatures, P dissociates into atomic P.
Phosphorus | Allotropes
The IUPAC accepts the D and T symbols, but recommends instead using standard isotopic symbols (H and H) to avoid confusion in the alphabetic sorting of chemical formulas. The ordinary isotope of hydrogen, with no neutrons, is sometimes called protium. (During the early study of radioactivity, some other heavy radioactive isotopes were given names, but such names are rarely used today.)
Isotopes of hydrogen | Introduction
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Table of nuclides (segmented, wide) | Isotopes for elements 30-59
These isotope tables show all of the known isotopes of the chemical elements, arranged with increasing atomic number from left to right and increasing neutron number from top to bottom. Half lives are indicated by the color of each isotope's cell (see color chart in each section). Colored borders indicate half lives of the most stable nuclear isomer states. The data for these tables came from Brookhaven National Laboratory which has an interactive Table of Nuclides with data on ~3000 nuclides.
Table of nuclides (segmented, narrow) | Introduction
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Table of nuclides (segmented, narrow) | Isotopes for elements 90-104
The β phase was produced in 1960 by hydrogen reduction of BBr on hot tungsten, rhenium or tantalum filaments at temperatures 1270–1550 °C (i.e. chemical vapor deposition). Further studies have reproduced the synthesis and confirmed the absence of impurities in this phase.
Allotropes of boron | β-tetragonal boron
An isotope and/or nuclide is specified by the name of the particular element (this indicates the atomic number) followed by a hyphen and the mass number (e.g. helium-3, helium-4, carbon-12, carbon-14, uranium-235 and uranium-239). When a chemical symbol is used, e.g. "C" for carbon, standard notation (now known as "AZE notation" because "A" is the mass number, "Z" the atomic number, and E for element) is to indicate the mass number (number of nucleons) with a superscript at the upper left of the chemical symbol and to indicate the atomic number with a subscript at the lower left (e.g. , , , , , and ).
Isotope | Notation
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Table of nuclides (segmented, narrow) | Isotopes for elements 30-44
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Table of nuclides (segmented, narrow) | Isotopes for elements 60-74
These isotope tables show all of the known isotopes of the chemical elements, arranged with increasing atomic number from left to right and increasing neutron number from top to bottom. Half lives are indicated by the color of each isotope's cell (see color chart in each section). Colored borders indicate half lives of the most stable nuclear isomer states. The data for these tables came from Brookhaven National Laboratory which has an interactive Table of Nuclides with data on ~3000 nuclides.
Table of nuclides (segmented, wide) | Introduction
Isotopes are distinguished by the atomic mass number (total protons and neutrons) for a particular isotope of an element, with this number combined with the pertinent element's symbol. IUPAC prefers that isotope symbols be written in superscript notation when practical, for example C and U. However, other notations, such as carbon-12 and uranium-235, or C-12 and U-235, are also used. As a special case, the three naturally occurring isotopes of the element hydrogen are often specified as H for H (protium), D for H (deuterium), and T for H (tritium). This convention is easier to use in chemical equations, replacing the need to write out the mass number for each atom.
Chemical element | Isotope symbols
Graphite is one of the allotropes of carbon. Graphite may also refer to:
Graphite (disambiguation) | Introduction
Diamane is a 2D form of diamond. It can be made via high pressures, but without that pressure, the material reverts to graphene. Another technique is to add hydrogen atoms but those bonds are weak. Using fluorine (xenon-difluoride) instead brings the layers closer together, strengthening the bonds. This is called f-diamane.
Allotropes of carbon | Diamane
Within a single element, the number of neutrons may vary, determining the isotope of that element. The total number of protons and neutrons determine the nuclide. The number of neutrons relative to the protons determines the stability of the nucleus, with certain isotopes undergoing radioactive decay. The proton, the electron, and the neutron are classified as fermions. Fermions obey the Pauli exclusion principle which prohibits "identical" fermions, such as multiple protons, from occupying the same quantum state at the same time. Thus, every proton in the nucleus must occupy a quantum state different from all other protons, and the same applies to all neutrons of the nucleus and to all electrons of the electron cloud.
Atom | Nucleus
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Table of nuclides (segmented, wide) | Isotopes for elements 60-89
This adduct is produced from a solution of cyclo-S and cyclo-S in CS. It has a density midway between cyclo-S and cyclo-S. The crystal consists of alternate layers of cyclo-S and cyclo-S. This material is a rare example of an allotrope that contains molecules of different sizes.
Allotropes of sulfur | "Cyclo"-S."cyclo"-S adduct
The diamond allotrope of carbon is clearly nonmetallic, being translucent and having a low electrical conductivity of 10 to 10 S·cm. Graphite has an electrical conductivity of 3 × 10 S·cm, a figure more characteristic of a metal. Phosphorus, sulfur, arsenic, selenium, antimony, and bismuth also have less stable allotropes that display different behaviours.
Metalloid | Allotropes
Oxygen's most common allotrope is diatomic oxygen, or O, a reactive paramagnetic molecule that is ubiquitous to aerobic organisms and has a blue color in its liquid state. Another allotrope is O, or ozone, which is three oxygen atoms bonded together in a bent formation. There is also an allotrope called tetraoxygen, or O, and six allotropes of solid oxygen including "red oxygen", which has the formula O. Sulfur has over 20 known allotropes, which is more than any other element except carbon. The most common allotropes are in the form of eight-atom rings, but other molecular allotropes that contain as few as two atoms or as many as 20 are known.
Chalcogen | Allotropes
Chemical elements are defined by their number of protons, but the mass of the atom is determined by the number of protons and neutrons in the nucleus. Isotopes are atoms that are of a specific element, but have different numbers of neutrons and thus different masses. In a specific object, you can have a ratio between two isotopes of an element. This ratio varies slightly in the world, so in order to study isotopic ratio changes across the world, changes in isotope ratios are defined as deviations from a standard, multiplied by 1000. This unit is a "per mil". As a convention, the ratio is of the heavier isotope to the lower isotope.
Environmental isotopes | Isotope Geochemistry
Nanotube-like and buckyball-like molecules composed of are known.
Molybdenum disulfide | Allotropes
The number of protons in a nucleus determine what element it belongs to: to have a neutral atom, the same number of electrons circulate around the atomic nucleus and these define the chemical properties of the element. However, a specific element can occur with different ‘nuclei’, each having the same number of protons but a different number of neutrons. These variations of the element are called its isotopes. For example, three isotopes of the element carbon are called carbon-12, carbon-13 and carbon-14; which have 6, 7, 8 neutrons respectively. The numbers added after the element name are the mass number of the isotope i.e.
On-Line Isotope Mass Separator | Background
Similarly, yellow arsenic is a molecular solid composed of As units. Some forms of sulfur and selenium are composed of S (or Se) units and are molecular solids at ambient conditions, but converted into covalent allotropes having atomic chains extending throughout the crystal.
Molecular solid | Allotropes
A nuclide is a species of an atom with a specific number of protons and neutrons in the nucleus, for example carbon-13 with 6 protons and 7 neutrons. The "nuclide" concept (referring to individual nuclear species) emphasizes nuclear properties over chemical properties, whereas the "isotope" concept (grouping all atoms of each element) emphasizes chemical over nuclear. The neutron number has large effects on nuclear properties, but its effect on chemical properties is negligible for most elements. Even for the lightest elements, whose ratio of neutron number to atomic number varies the most between isotopes, it usually has only a small effect although it matters in some circumstances (for hydrogen, the lightest element, the isotope effect is large enough to affect biology strongly).
Isotope | Isotope vs. nuclide
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Table of nuclides (segmented, narrow) | Isotopes for elements 105-118
All group 3 elements have an odd atomic number, and therefore few stable isotopes. Scandium has one stable isotope, and yttrium itself has only one stable isotope, Y, which is also the only isotope that occurs naturally. However, the lanthanide rare earths contain elements of even atomic number and many stable isotopes. Yttrium-89 is thought to be more abundant than it otherwise would be, due in part to the s-process, which allows enough time for isotopes created by other processes to decay by electron emission (neutron → proton). Such a slow process tends to favor isotopes with atomic mass numbers (A = protons + neutrons) around 90, 138 and 208, which have unusually stable atomic nuclei with 50, 82, and 126 neutrons, respectively.
Yttrium | Isotopes and nucleosynthesis
Its behavior is that of a hydrogen atom and not a noble helium atom.
Isotopes of hydrogen | Hydrogen-4.1
The quasi-equilibrium produces radioactive isobars Ti, Cr, Fe, and Ni, which (except Ti) are created in abundance but decay after the explosion and leave the most stable isotope of the corresponding element at the same atomic weight. The most abundant and extant isotopes of elements produced in this way are Ti, Cr, and Fe. These decays are accompanied by the emission of gamma-rays (radiation from the nucleus), whose spectroscopic lines can be used to identify the isotope created by the decay. The detection of these emission lines were an important early product of gamma-ray astronomy.
Nucleosynthesis | Explosive nucleosynthesis
The molecule in question is made up of a radioactive isotope of aluminium with 13 protons and 13 neutrons bound together with atoms of fluorine.
CK Vulpeculae | Properties
This stands in contrast to the well-characterised cationic and anionic polynitrogens azide (), pentazenium (), and pentazolide (cyclic aromatic ). Under extremely high pressures (1.1 million atm) and high temperatures (2000 K), as produced in a diamond anvil cell, nitrogen polymerises into the single-bonded cubic gauche crystal structure. This structure is similar to that of diamond, and both have extremely strong covalent bonds, resulting in its nickname "nitrogen diamond". At atmospheric pressure, molecular nitrogen condenses (liquefies) at 77 K (−195.79 °C) and freezes at 63 K (−210.01 °C) into the beta hexagonal close-packed crystal allotropic form. Below 35.4 K (−237.6 °C) nitrogen assumes the cubic crystal allotropic form (called the alpha phase).
Nitrogen | Allotropes
The majority of stable nuclides are even-proton-even-neutron, where all numbers "Z", "N", and "A" are even. The odd-"A" stable nuclides are divided (roughly evenly) into odd-proton-even-neutron, and even-proton-odd-neutron nuclides. Stable odd-proton-odd-neutron nuclei are the least common.
Isotope | Even and odd nucleon numbers
As molten iron cools down, it solidifies at 1,538 °C (2,800 °F) into its δ allotrope, which has a body-centered cubic (BCC) crystal structure. δ-iron can dissolve as much as 0.08% of carbon by mass at 1,475 °C.
Allotropes of iron | Delta iron (δ-Fe)
Allotropes are different structural forms of the same element and can exhibit quite different physical properties and chemical behaviours. The change between allotropic forms is triggered by the same forces that affect other structures, i.e., pressure, light, and temperature. Therefore, the stability of the particular allotropes depends on particular conditions. For instance, iron changes from a body-centered cubic structure (ferrite) to a face-centered cubic structure (austenite) above 906 °C, and tin undergoes a modification known as tin pest from a metallic form to a semiconductor form below 13.2 °C (55.8 °F). As an example of allotropes having different chemical behaviour, ozone (O) is a much stronger oxidizing agent than dioxygen (O).
Allotropy | Differences in properties of an element's allotropes
The temperature of the phase transition is believed to be quite close to the melting point.
Berkelium | Allotropes
It gradually oxidizes when exposed to water in the presence of oxygen, which is a concern when contemplating it as a material for the manufacture of transistors, for example.
Allotropes of phosphorus | Phosphorene
Although isotopes are more relevant to nuclear chemistry or stable isotope chemistry than to conventional chemistry, different isotopes may be indicated with a prefixed superscript in a chemical formula. For example, the phosphate ion containing radioactive phosphorus-32 is [PO]. Also a study involving stable isotope ratios might include the molecule OO. A left-hand subscript is sometimes used redundantly to indicate the atomic number. For example, O for dioxygen, and for the most abundant isotopic species of dioxygen. This is convenient when writing equations for nuclear reactions, in order to show the balance of charge more clearly.
Chemical formula | Isotopes
Actinides with odd neutron number are generally fissile (with thermal neutrons), whereas those with even neutron number are generally not, though they are fissionable with fast neutrons. All observationally stable odd-odd nuclides have nonzero integer spin. This is because the single unpaired neutron and unpaired proton have a larger nuclear force attraction to each other if their spins are aligned (producing a total spin of at least 1 unit), instead of anti-aligned. See deuterium for the simplest case of this nuclear behavior. Only , and have odd neutron number and are the most naturally abundant isotope of their element.
Isotope | Odd neutron number
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Table of nuclides (segmented, narrow) | Isotopes for elements 75-89
The term "allotropy" is used for elements only, not for compounds. The more general term, used for any crystalline material, is polymorphism. Allotropy refers only to different forms of an element within the same phase (i.e.: solid, liquid or gas states); the differences between these states would not alone constitute examples of allotropy. For some elements, allotropes have different molecular formulae despite difference in phase; for example, two allotropes of oxygen (dioxygen, O, and ozone, O) can both exist in the solid, liquid and gaseous states. Other elements do not maintain distinct allotropes in different phases; for example, phosphorus has numerous solid allotropes, which all revert to the same P form when melted to the liquid state.
Allotropy | Introduction
Owing to both of these advantages, the method of isotope dilution is regarded among chemistry measurement methods of the highest metrological standing. Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of a given element have the same number of protons in each atom. The term "isotope" is formed from the Greek roots "isos" (ἴσος "equal") and "topos" (τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table.
Isotope dilution | Introduction
Upon further compression to 25 GPa, berkelium transforms to an orthorhombic γ-berkelium structure similar to that of α-uranium. This transition is accompanied by a 12% volume decrease and delocalization of the electrons at the 5f electron shell. No further phase transitions are observed up to 57 GPa. Upon heating, α-berkelium transforms into another phase with an "fcc" lattice (but slightly different from β-berkelium), space group "Fmm" and the lattice constant of 500 pm; this "fcc" structure is equivalent to the closest packing with the sequence ABC. This phase is metastable and will gradually revert to the original α-berkelium phase at room temperature.
Berkelium | Allotropes
Atoms with the same atomic number but different neutron numbers, and hence different mass numbers, are known as isotopes. A little more than three-quarters of naturally occurring elements exist as a mixture of isotopes (see monoisotopic elements), and the average isotopic mass of an isotopic mixture for an element (called the relative atomic mass) in a defined environment on Earth, determines the element's standard atomic weight. Historically, it was these atomic weights of elements (in comparison to hydrogen) that were the quantities measurable by chemists in the 19th century.
Atomic number | Introduction
Recent studies suggest that an effect called superlubricity can also account for this effect.
Allotropes of carbon | Graphite
Plutonium normally has six allotropes and forms a seventh (zeta, ζ) at high temperature within a limited pressure range. These allotropes, which are different structural modifications or forms of an element, have very similar internal energies but significantly varying densities and crystal structures. This makes plutonium very sensitive to changes in temperature, pressure, or chemistry, and allows for dramatic volume changes following phase transitions from one allotropic form to another. The densities of the different allotropes vary from 16.00 g/cm to 19.86 g/cm. The presence of these many allotropes makes machining plutonium very difficult, as it changes state very readily.
Plutonium | Allotropes
Plutonium in the δ phase ("delta phase") normally exists in the 310 °C to 452 °C range but is stable at room temperature when alloyed with a small percentage of gallium, aluminium, or cerium, enhancing workability and allowing it to be welded in weapons applications. The delta phase has more typical metallic character, and is roughly as strong and malleable as aluminium. In fission weapons, the explosive shock waves used to compress a plutonium core will also cause a transition from the usual delta phase plutonium to the denser alpha phase, significantly helping to achieve supercriticality. The plutonium-gallium alloy is the most common δ-stabilized alloy.
Allotropes of plutonium | Stabilization
For example, although the neutron:proton ratio of is 1:2, the neutron:proton ratio of is greater than 3:2. A number of lighter elements have stable nuclides with the ratio 1:1 ("Z" = "N"). The nuclide (calcium-40) is observationally the heaviest stable nuclide with the same number of neutrons and protons. All stable nuclides heavier than calcium-40 contain more neutrons than protons.
Isotope | Nuclear properties and stability
Carbon has multiple allotropes. The most common is graphite, which is carbon in the form of stacked sheets. Another form of carbon is diamond, but this is relatively rare. Amorphous carbon is a third allotrope of carbon; it is a component of soot. Another allotrope of carbon is a fullerene, which has the form of sheets of carbon atoms folded into a sphere. A fifth allotrope of carbon, discovered in 2003, is called graphene, and is in the form of a layer of carbon atoms arranged in a honeycomb-shaped formation. Silicon has two known allotropes that exist at room temperature.
Carbon group | Allotropes
Most (66 of 94) naturally occurring elements have more than one stable isotope. Except for the isotopes of hydrogen (which differ greatly from each other in relative mass—enough to cause chemical effects), the isotopes of a given element are chemically nearly indistinguishable. All of the elements have some isotopes that are radioactive (radioisotopes), although not all of these radioisotopes occur naturally. The radioisotopes typically decay into other elements upon radiating an alpha or beta particle. If an element has isotopes that are not radioactive, these are termed "stable" isotopes. All of the known stable isotopes occur naturally (see primordial isotope).
Chemical element | Isotopes
Nanobuds were first reported in 2007 and are hybrid buckytube/buckyball materials (buckyballs are covalently bonded to the outer wall of a nanotube) that combine the properties of both in a single structure.
Carbon | Allotropes
Examples include P. red phosphorus ; As, amorphous arsenic.
IUPAC nomenclature of inorganic chemistry 2005 | Amorphous recognised allotropes
Adding Gamma loop additives keeps the iron in a body-centered cubic structure and prevents the steel from suffering phase transition to other solid states.
Allotropes of iron | Structural phase transitions
Cyclopropatriene is a hypothetical allotrope of carbon that was once proposed as a candidate for a spectroscopically observed tricarbon species. It is a cyclic cumulene.
Cyclopropatriene | Introduction
Unlike carbon aerogels, carbon nanofoam is a poor electrical conductor.
Allotropes of carbon | Carbon nanofoam
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Table of nuclides (segmented, wide) | Isotopes for elements 90-118
Apart from the isotopes Y, Y, and Y, with half-lives of 58.51 days, 79.8 hours, and 64 hours, respectively, all the other isotopes have half-lives of less than a day and most of less than an hour.
Yttrium | Isotopes and nucleosynthesis
Many isotopes are produced in cyclotrons, for example fluorine-18 and oxygen-15 which are widely used for positron emission tomography.
Synthetic radioisotope | Production
As the fused nuclei cool to the ground state, they require emission of only one or two neutrons, thus allowing for the generation of more neutron-rich products. The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see cold fusion). The table below contains various combinations of targets and projectiles which could be used to form compound nuclei with "Z" = 107.
Isotopes of bohrium | Nucleosynthesis