query: the main difference between isotopes of the same element

pos: Isotope 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. For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 respectively. The atomic number of carbon is 6, which means that every carbon atom has 6 protons, so that

neg: Isotope fractionation Isotope fractionation Isotope fractionation describes processes that affect the relative abundance of isotopes, often used in isotope geochemistry. Normally, the focus is on stable isotopes of the same element. Isotopic fractionation in the natural environment can be measured by isotope analysis, using isotope-ratio mass spectrometry, to separate different element isotopes on the basis of their mass-to-charge ratio, an important tool to understand natural systems. For example, in biochemistry processes cause a fluctuation in the amount of isotopes of carbon ratios incorporated into a biological being. The difference between the true amount of carbon and the amount in the plant is

neg: Chemical element 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". 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

neg: Isotope 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

neg: Mass number The difference between mass number of an atom and its isotopic mass is known as the mass excess. Mass excess should not be confused with mass defect which is the difference between the mass of an atom and its constituent particles (namely protons, neutrons and electrons). There are two reasons for mass defect/excess: The mass number should also not be confused with the standard atomic weight (also called atomic weight) of an element, which is the ratio of the average atomic mass of the different isotopes of that element (weighted by abundance) to the unified atomic mass unit. The atomic

neg: Isotope the heaviest stable nuclide with the same number of neutrons and protons; (theoretically, the heaviest stable one is sulfur-32). All stable nuclides heavier than calcium-40 contain more neutrons than protons. Of the 80 elements with a stable isotope, the largest number of stable isotopes observed for any element is ten (for the element tin). No element has nine stable isotopes. Xenon is the only element with eight stable isotopes. Four elements have seven stable isotopes, eight have six stable isotopes, ten have five stable isotopes, nine have four stable isotopes, five have three stable isotopes, 16 have two stable isotopes

neg: Isotope Uranium isotopes have been separated in bulk by gas diffusion, gas centrifugation, laser ionization separation, and (in the Manhattan Project) by a type of production mass spectrometry. Isotope Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in mass 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

neg: Isotope Isotope Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in mass 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. The number of protons within the atom's nucleus is called atomic number and is equal to the number of

neg: Isotope dilution employs signal ratios. Owing to both of these advantages, the method of isotope dilution is regarded among chemistry measurement methods of the highest metrological standing. What is Isotope? 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. Analytical application

neg: Atom between atoms. By this mechanism, atoms are able to bond into molecules and other types of chemical compounds like ionic and covalent network crystals. By definition, any two atoms with an identical number of "protons" in their nuclei belong to the same chemical element. Atoms with equal numbers of protons but a different number of "neutrons" are different isotopes of the same element. For example, all hydrogen atoms admit exactly one proton, but isotopes exist with no neutrons (hydrogen-1, by far the most common form, also called protium), one neutron (deuterium), two neutrons (tritium) and more than two neutrons. The

neg: Isotope neutron number to atomic number varies the most between isotopes it usually has only a small effect, although it does matter in some circumstances (for hydrogen, the lightest element, the isotope effect is large enough to strongly affect biology). The term "isotopes" (originally also "isotopic elements", now sometimes "isotopic nuclides") is intended to imply comparison (like "synonyms" or "isomers"), for example: the nuclides , , are isotopes (nuclides with the same atomic number but different mass numbers), but , , are isobars (nuclides with the same mass number). However, because "isotope" is the older term, it is better known than

neg: Isomeric shift levels E, followed by emission of photons. Atomic levels are a manifestation of the electromagnetic interaction between electrons and nuclei. The energy levels of two atoms the nuclei of which are different isotopes of the same element are shifted one with respect to the other, despite the fact that the electric charges Z of the two isotopes are identical. This is so because isotopes differ by the number of neutrons and therefore the masses and volumes of two isotopes are different; these differences give rise to the isotopic shift on atomic spectral lines. In the case of two nuclear isomers

neg: Methane clumped isotopes isotopologues of natural abundance was made in 2014. This is a very young and fast-growing field. The Δ notation of clumped isotopes is an analogue to δ notation of traditional isotopes (e.g. "δ"C, "δ"O, "δ"N, δS and "δ"D). The notation of traditional isotopes are defined as: formula_1‰ formula_2 is the ratio of the rare isotope to the abundant isotope in the sample. formula_3 is the same ratio in the reference material. Because the variation of formula_2 is rather small, in the convenience of comparison between difference samples, the notation is define as a ratio minus 1 and expressed in permil

neg: Isotope fractionation become enriched in the liquid phase while the lighter isotopes (O and H) tend toward the vapor phase. Isotope fractionation Isotope fractionation describes processes that affect the relative abundance of isotopes, often used in isotope geochemistry. Normally, the focus is on stable isotopes of the same element. Isotopic fractionation in the natural environment can be measured by isotope analysis, using isotope-ratio mass spectrometry, to separate different element isotopes on the basis of their mass-to-charge ratio, an important tool to understand natural systems. For example, in biochemistry processes cause a fluctuation in the amount of isotopes of carbon ratios incorporated into

neg: Nuclear binding energy Only under conditions of extreme pressure and temperature (for example, within the core of a star), can such a process take place. There are around 94 naturally occurring elements on earth. The atoms of each element have a nucleus containing a specific number of protons (always the same number for a given element), and some number of neutrons, which is often roughly a similar number. Two atoms of the same element having different numbers of neutrons are known as isotopes of the element. Different isotopes may have different properties - for example one might be stable and another might be

neg: Stable isotope ratio Stable isotope ratio The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundance of such stable isotopes can be measured experimentally (isotope analysis), yielding an isotope ratio that can be used as a research tool. Theoretically, such stable isotopes could include the radiogenic daughter products of radioactive decay, used in radiometric dating. However, the expression stable-isotope ratio is preferably used to refer to isotopes whose relative abundances are affected by

neg: Isotopic labeling atoms in the products' structure to be determined. With information on the positioning of the isotopic atoms in the products, the reaction pathway the initial metabolites utilize to convert into the products can be determined. Radioactive isotopes can be tested using the autoradiographs of gels in gel electrophoresis. The radiation emitted by compounds containing the radioactive isotopes darkens a piece of photographic film, recording the position of the labeled compounds relative to one another in the gel. Isotope tracers are commonly used in the form of isotope ratios. By studying the ratio between two isotopes of the same element, we

neg: Stable isotope ratio non-breeding season. Numerous ecological studies have also used isotope analyses to understand migration, food-web structure, diet, and resource use in sea turtles. Stable isotope ratio The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element. Hence, the plural form stable isotopes usually refers to isotopes of the same element. The relative abundance of such stable isotopes can be measured experimentally (isotope analysis), yielding an isotope ratio that can be used as a research tool. Theoretically, such stable isotopes could include the radiogenic daughter products of radioactive decay,

neg: Isotope-ratio mass spectrometry has an array of Faraday cups, which allows the simultaneous detection of multiple isotopes. Measurement of natural variations in the abundances of stable isotopes of the same element is normally referred to as stable isotope analysis. This field is of interest because the differences in mass between different isotopes leads to isotope fractionation, causing measurable effects on the isotopic composition of samples, characteristic of their biological or physical history. As a specific example, the hydrogen isotope deuterium (heavy hydrogen) is almost double the mass of the common hydrogen isotope. Water molecules containing the common hydrogen isotope (and the common oxygen

neg: Chemical element 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. Of the 80 elements with at least one stable isotope, 26 have only one single stable isotope. The mean number of stable isotopes for the 80 stable elements is 3.1 stable isotopes per element. The largest number of stable isotopes that occur for a single element is 10 (for tin, element 50). The mass number of an element, "A", is the number of nucleons (protons and neutrons) in the atomic nucleus. Different isotopes

neg: Atomic mass more significant figures than atomic weights. Standard atomic weight is related to atomic mass by the abundance ranking of isotopes for each element. It is usually "about" the same value as the atomic mass of the most abundant isotope, other than what looks like (but is not actually) a rounding difference. The atomic mass of atoms, ions, or atomic nuclei is slightly less than the sum of the masses of their constituent protons, neutrons, and electrons, due to binding energy mass loss (as per "E"="mc"). Relative "isotopic" mass (a property of a single atom) is not to be confused with

neg: Geochemistry difference in masses is a larger fraction of the total mass. Ratios between isotopes are generally compared to a standard. For example, sulfur has four stable isotopes, of which the two most common are S and S. The ratio of their concentrations, , is reported as where is the same ratio for a standard. Because the differences are small, the ratio is multiplied by 1000 to make it parts per thousand (referred to as parts per mil). This is represented by the symbol . "Equilibrium fractionation" occurs between chemicals or phases that are in equilibrium with each other. In equilibrium

neg: Rutherfordium suggested for element 106 and IUPAC felt that the Dubna team should be rightly recognized for their contributions. However, there was still a dispute over the names of elements 104–107. In 1997 the teams involved resolved the dispute and adopted the current name "rutherfordium". The name "dubnium" was given to element 105 at the same time. Rutherfordium 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. Sixteen different isotopes have been reported with atomic masses from 253 to 270 (with

neg: Isotopes of tennessine Isotopes of tennessine Tennessine (Ts) is the most-recently synthesized synthetic element, and much of the data is hypothetical. As for any synthetic element, a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first (and so far only) isotopes to be synthesized were Ts and Ts in 2009. The longer-lived isotope is Ts with a half-life of 51 ms. The below table contains various combinations of targets and projectiles that could be used to form compound nuclei with atomic number 117. Between July 2009 and February 2010, the team at the JINR (Flerov

neg: Period 5 element blood cells in the body. Tin is a chemical element with the symbol Sn (for ) and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest number of stable isotopes in the periodic table. Tin is obtained chiefly from the mineral cassiterite, where it occurs as tin dioxide, SnO. This silvery, malleable

neg: Chemical element these numbers are integers), and also resolves some ambiguities in the chemistry-based view due to varying properties of isotopes and allotropes within the same element. Currently, IUPAC defines an element to exist if it has isotopes with a lifetime longer than the 10 seconds it takes the nucleus to form an electronic cloud. By 1914, seventy-two elements were known, all naturally occurring. The remaining naturally occurring elements were discovered or isolated in subsequent decades, and various additional elements have also been produced synthetically, with much of that work pioneered by Glenn T. Seaborg. In 1955, element 101 was discovered and

neg: Timeline of natural history origin (currently estimated to have been some 4,600 million years ago) to the present day. Radiometric dating measures the steady decay of radioactive elements in an object to determine its age. It is used to calculate dates for the older part of the planet's geological record. The theory is very complicated but, in essence, the radioactive elements within an object decay to form isotopes of each chemical element. Isotopes are atoms of the element that differ in mass but share the same general properties. Geologists are most interested in the decay of isotopes carbon-14 (into nitrogen-14) and potassium-40 (into argon-40).

neg: Isotopic resonance hypothesis in 1921 (awarded in 1922). The question of stable, non-radioactive isotopes was more difficult and required the development by Francis Aston of a high-resolution mass spectrograph, which allowed the separation of different stable isotopes of one and the same element. Francis Aston was awarded the 1922 Nobel Prize in Chemistry for this achievement. With his enunciation of the whole-number rule, Aston solved a problem that had riddled chemistry for a hundred years. The understanding was that different isotopes of a given element would be chemically identical. It was discovered in 1930s<ref name=zubarev/2 by Harold Urey in 1932 (awarded the Nobel

neg: Promethium years. Almost 20 years later, it was claimed that the element occurs in natural neodymium in equilibrium in quantities below 10 grams of promethium per one gram of neodymium. However, these observations were disproved by newer investigations, because for all seven naturally occurring neodymium isotopes, any single beta decays (which can produce promethium isotopes) are forbidden by energy conservation. In particular, careful measurements of atomic masses show that the mass difference Nd-Pm is negative (−87 keV), which absolutely prevents the single beta decay of Nd to Pm. In 1965 Olavi Erämetsä separated out traces of Pm from a rare earth

neg: Neutron scattering length titanium and nickel, it is possible to mix isotopes of an element whose lengths are of opposite signs to give a net scattering length of zero, in which case "coherent" scattering will not occur at all. However, neutrons will still undergo strong incoherent scattering in these materials. There is a large difference in scattering length between protium (-0.374) and deuterium (0.667). This means that protium, the most common isotope of hydrogen, is poorly imaged due to its smaller absolute magnitude and because its scattering density tends to cancel that of adjacent carbon, nitrogen, or oxygen, which have positive scattering lengths.

neg: Atomic mass exactly halfway between two integral multiples of that of hydrogen. Still later, this was shown to be largely due to a mix of isotopes, and that the atomic masses of pure isotopes, or nuclides, are multiples of the hydrogen mass, to within about 1%. In the 1860s Stanislao Cannizzaro refined relative atomic masses by applying Avogadro's law (notably at the Karlsruhe Congress of 1860). He formulated a law to determine relative atomic masses of elements: "the different quantities of the same element contained in different molecules are all whole multiples of the atomic weight" and determined relative atomic masses and

neg: Geochemistry mass. Atoms with the same atomic number but different neutron numbers are called isotopes. A given isotope is identified by a letter for the element preceded by a superscript for the mass number. For example, two common isotopes of chlorine are Cl and Cl. There are about 1700 known combinations of Z and N, of which only about 260 are stable. However, most of the unstable isotopes do not occur in nature. In geochemistry, stable isotopes are used to trace chemical pathways and reactions, while isotopes are primarily used to date samples. The chemical behavior of an atom – its

neg: Chemical element 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). 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

neg: Isodiapher Isodiapher In nuclear physics and radioactivity, isodiaphers refers to nuclides which have different atomic numbers and mass numbers but the same neutron excess, which is the difference between numbers of neutrons and protons in the nucleus. For example, for both and the difference between the neutron number ("N") and proton number ("Z") is "N" − "Z" = 54. One large family of isodiaphers has zero neutron excess, "N"="Z". It contains many primordial isotopes of elements up to calcium. It includes ubiquitous , , and . The daughter nuclide of an alpha decay is an isodiapher of the original nucleus. Similarly,

neg: Isodiapher beta decays (and other weak-force-involving decays) produce isobars. Isodiapher In nuclear physics and radioactivity, isodiaphers refers to nuclides which have different atomic numbers and mass numbers but the same neutron excess, which is the difference between numbers of neutrons and protons in the nucleus. For example, for both and the difference between the neutron number ("N") and proton number ("Z") is "N" − "Z" = 54. One large family of isodiaphers has zero neutron excess, "N"="Z". It contains many primordial isotopes of elements up to calcium. It includes ubiquitous , , and . The daughter nuclide of an alpha decay

neg: Paleothermometer isotopes is lower, so vapour contains relatively more of the lighter isotopes and when the vapour condenses the precipitation preferentially contains heavier isotopes. The difference from SMOW is expressed as and a similar formula for δD. values for precipitation are always negative. The major influence on is the difference between ocean temperatures where the moisture evaporated and the place where the final precipitation occurred; since ocean temperatures are relatively stable the value mostly reflects the temperature where precipitation occurs. Taking into account that the precipitation forms above the inversion layer, we are left with a linear relation: which is empirically

neg: Tin Tin Tin is a chemical element with the symbol Sn (from ) and atomic number 50. It is a post-transition metal in group 14 of the periodic table of elements. It is obtained chiefly from the mineral cassiterite, which contains stannic oxide, SnO. Tin shows a chemical similarity to both of its neighbors in group 14, germanium and lead, and has two main oxidation states, +2 and the slightly more stable +4. Tin is the 49th most abundant element and has, with 10 stable isotopes, the largest number of stable isotopes in the periodic table, thanks to its magic number

neg: Atom one stable isotope exists. As a rule, there is only a handful of stable isotopes for each of these elements, the average being 3.2 stable isotopes per element. Twenty-six elements have only a single stable isotope, while the largest number of stable isotopes observed for any element is ten, for the element tin. Elements 43, 61, and all elements numbered 83 or higher have no stable isotopes. Stability of isotopes is affected by the ratio of protons to neutrons, and also by the presence of certain "magic numbers" of neutrons or protons that represent closed and filled quantum shells. These

neg: Isotopes of beryllium Isotopes of beryllium Beryllium (Be) has 12 known isotopes, but only one of these isotopes () is stable and a primordial nuclide. As such, beryllium is considered a monoisotopic element. It is also a mononuclidic element, because its other isotopes have such short half-lives that none are primordial and their abundance is very low (standard atomic weight is 9.0122). Beryllium is unique as being the only monoisotopic element with both an even number of protons and an odd number of neutrons. There are 25 other monoisotopic elements but all have odd atomic numbers, and even numbers of neutrons. Of the

neg: Unbinilium is expected to decay via a cascade of alpha decays leading to spontaneous fission around copernicium, the total half-lives of unbinilium isotopes are also predicted to be measured in microseconds. This has consequences for the synthesis of unbinilium, as isotopes with half-lives below one microsecond would decay before reaching the detector. Nevertheless, new theoretical models show that the expected gap in energy between the proton orbitals 2f (filled at element 114) and 2f (filled at element 120) is smaller than expected, so that element 114 no longer appears to be a stable spherical closed nuclear shell, and this energy gap

neg: Isotopes of neodymium This element also has 13 known meta states with the most stable being Nd (t 5.5 hours), Nd (t 5.5 minutes) and Nd (t ~70 seconds). The primary decay modes before the most abundant stable isotope, Nd, are electron capture and positron decay, and the primary mode after is beta decay. The primary decay products before Nd are element Pr (praseodymium) isotopes and the primary products after are element Pm (promethium) isotopes. Isotopes of neodymium Naturally occurring neodymium (Nd) is composed of 5 stable isotopes, Nd, Nd, Nd, Nd and Nd, with Nd being the most abundant (27.2% natural abundance),

neg: Numerical partial differential equations to numerically solve certain differential equations, often involving the use of the Fast Fourier Transform. The idea is to write the solution of the differential equation as a sum of certain "basis functions" (for example, as a Fourier series, which is a sum of sinusoids) and then to choose the coefficients in the sum that best satisfy the differential equation. Spectral methods and finite element methods are closely related and built on the same ideas; the main difference between them is that spectral methods use basis functions that are nonzero over the whole domain, while finite element methods use basis

neg: Nuclear power plant and is found in sea water as well as most rocks. Naturally occurring uranium is found in two different isotopes: uranium-238 (U-238), accounting for 99.3% and uranium-235 (U-235) accounting for about 0.7%. Isotopes are atoms of the same element with a different number of neutrons. Thus, U-238 has 146 neutrons and U-235 has 143 neutrons. Different isotopes have different behaviours. For instance, U-235 is fissile which means that it is easily split and gives off a lot of energy making it ideal for nuclear energy. On the other hand, U-238 does not have that property despite it being the same

neg: Hydrogen isotope biogeochemistry broken in the reaction. Since different isotopes have different masses, the bond energies are different between different isotopologues of a chemical species. This will result in a difference in the rate of a reaction for the different isotopologues, resulting in a fractionation of the different isotopes between the reactant and product in a chemical reaction. This is known as the kinetic isotope effect. A classic example of such an isotope effect is the D/H ratio difference in the equilibrium between HO and H which can have an alpha value of as much as 3-4. In many areas of study the

neg: Promethium drop model and stabilities of neighbor element isotopes; it is also the least stable element of the first 84. The primary decay products are neodymium and samarium isotopes (promethium-146 decays to both, the lighter isotopes generally to neodymium via positron decay and electron capture, and the heavier isotopes to samarium via beta decay). Promethium nuclear isomers may decay to other promethium isotopes and one isotope (Pm) has a very rare alpha decay mode to stable praseodymium-141. The most stable isotope of the element is promethium-145, which has a specific activity of and a half-life of 17.7 years via electron capture.

neg: Environmental isotopes Environmental isotopes The environmental isotopes are a subset of the isotopes, both stable and radioactive, which are the object of isotope geochemistry. They are primarily used as tracers to see how things move around within the ocean-atmosphere system, within terrestrial biomes, within the Earth's surface, and between these broad domains. 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,

neg: Isotopes of technetium isotope of technetium, since there can be only one stable nuclide with a fixed odd number of nucleons. For the isotopes with an even number of nucleons, since technetium has an odd number of protons, any isotope must also have an odd number of neutrons. In such a case, the presence of a stable nuclide having the same number of nucleons and an even number of protons rules out the possibility of a stable nucleus. Isotopes of technetium Technetium (Tc) is the first of the two elements lighter than bismuth that have no non-radioactive isotopes; the other such element is

neg: Table of nuclides nuclides, as it distinguishes the isotopes of an element. It contrasts with a periodic table, which only maps their chemical behavior, since isotopes (nuclides which are variants of the same element) do not differ chemically to any significant degree, with the exception of hydrogen. Nuclide charts organize nuclides along the X axis by their numbers of neutrons and along the Y axis by their numbers of protons, out to the limits of the neutron and proton drip lines. This representation was first published by Kurt Guggenheimer in 1934 and expanded by Giorgio Fea in 1935, Emilio Segrè in 1945 or

neg: Iron more into the inert core by the nucleus; however, they are higher than the values for the previous element manganese because that element has a half-filled 3d subshell and consequently its d-electrons are not easily delocalized. This same trend appears for ruthenium but not osmium. Naturally occurring iron consists of four stable isotopes: 5.845% of Fe, 91.754% of Fe, 2.119% of Fe and 0.282% of Fe. Of these stable isotopes, only Fe has a nuclear spin (−). The nuclide Fe theoretically can undergo double electron capture to Cr, but the process has never been observed and only a lower limit

neg: Clause of the distinctions presented above are represented in syntax trees. These trees make the difference between main and subordinate clauses very clear, and they also illustrate well the difference between argument and adjunct clauses. The following dependency grammar trees show that embedded clauses are dependent on an element in the main clause, often on a verb: The main clause encompasses the entire tree each time, whereas the embedded clause is contained within the main clause. These two embedded clauses are arguments. The embedded "wh"-clause "what we want" is the object argument of the predicate "know". The embedded clause "that he

neg: Nuclide matter in some circumstances (for hydrogen, the lightest element, the isotope effect is large enough to strongly affect biological systems). Since isotope is the older term, it is better known than nuclide, and is still sometimes used in contexts where nuclide might be more appropriate, such as nuclear technology and nuclear medicine. Although the words nuclide and isotope are often used interchangeably, being isotopes is actually only one relation between nuclides. The following table names some other relations. A set of nuclides with equal proton number (atomic number), i.e., of the same chemical element but different neutron numbers, are called

neg: Neutron cross section scattering and incoherent scattering, which is caused by the spin dependence of the scattering cross-section and, for a natural sample, presence of different isotopes of the same element in the sample. Because neutrons interact with the nuclear potential, the scattering cross-section varies for different isotopes of the element in question. A very prominent example is hydrogen and its isotope deuterium. The total cross-section for hydrogen is over 10 times that of deuterium, mostly due to the large incoherent scattering length of hydrogen. Metals tend to be rather transparent to neutrons, aluminum and zirconium being the two best examples of this.

neg: Isotopes of fluorine Isotopes of fluorine Fluorine (F) has 18 known isotopes, with atomic masses ranging from F to F, and including two isomers (F and F). However, of all those isotopes, only fluorine-19 either is stable, or has a long half-life. Effectively therefore, fluorine is a monoisotopic element and only artificially produced fluorine isotopes have atomic masses other than 19. The longest-lived radioisotope is F; and it has a half-life of only 109.771 minutes. All other fluorine isotopes have half-lives of less than a minute, and most of those less than a second, so that fluorine is a mononuclidic element for practical

neg: Electron capture valence electrons that are close to the nucleus, and also in orbitals with no orbital angular momentum. Electrons in s orbitals (regardless of shell or primary quantum number), have a probability antinode at the nucleus, and are thus far more subject to electron capture than p or d electrons, which have a probability node at the nucleus. Around the elements in the middle of the periodic table, isotopes that are lighter than stable isotopes of the same element tend to decay through electron capture, while isotopes heavier than the stable ones decay by electron emission. Electron capture happens most often

neg: Soil respiration preferentially. Isotopes are the same element that differ in the number of neutrons, thereby making one isotope heavier than the other. The two stable carbon isotopes are C and C. The C pathway will discriminate against the heavier isotope more than the C pathway. This will make the plant structures produced from C plants more enriched in the heavier isotope and therefore root exudates and litter from these plants will also be more enriched. When the carbon in these structures is respired, the CO will show a similar ratio of the two isotopes. Researchers will grow a C plant on

neg: Mattauch isobar rule Mattauch isobar rule The Mattauch isobar rule, formulated by Josef Mattauch in 1934, states that if two adjacent elements on the periodic table have isotopes of the same mass number, one of these isotopes must be radioactive. Two nuclides that have the same mass number (isobars) can both be stable only if their atomic numbers differ by more than one (In fact, for currently observationally stable nuclides, the difference can only be 2 or 4, and in theory, two nuclides that have the same mass number cannot be both stable (at least to beta decay or double beta decay), but

neg: Meitnerium isotopes Mt and Mt have half-lives of 0.72 and 0.44 seconds respectively. The remaining four isotopes have half-lives between 1 and 20 milliseconds. Some unknown isotopes, such as Mt, Mt, and Mt, are predicted to have half-lives longer than the known isotopes. Before their discovery, Mt and Mt were predicted to have half-lives of 20 seconds and 1 minute respectively, but they were later found to have half-lives of only 0.44 seconds and 5 milliseconds respectively. Meitnerium is the seventh member of the 6d series of transition metals. Since element 112 (copernicium) has been shown to be a group 12

neg: Isotopes of nitrogen isotopes of carbon, while most of the isotopes with masses above 15 decay to isotopes of oxygen. The shortest-lived known isotope is nitrogen-10, with a half-life of about 2.3 microseconds. Nitrogen-14 is one of two stable (non-radioactive) isotopes of the chemical element nitrogen, which makes about 99.636% of natural nitrogen. Nitrogen-14 is one of the very few stable nuclides with both an odd number of protons and of neutrons (seven each) and is the only one to make up a majority of its element. Each of proton or neutron contributes a nuclear spin of plus or minus spin 1/2, giving

neg: Isotopes of terbium decay mode before the most abundant stable isotope, Tb, is electron capture, and the primary mode behind is beta decay. The primary decay products before Tb are element Gd (gadolinium) isotopes, and the primary products behind are element Dy (dysprosium) isotopes. Isotopes of terbium Naturally occurring terbium (Tb) is composed of 1 stable isotope, Tb. Thirty-six radioisotopes have been characterized, with the most stable being Tb with a half-life of 180 years, Tb with a half-life of 71 years, and Tb with a half-life of 72.3 days. All of the remaining radioactive isotopes have half-lives that are less than 6.907

neg: Isotopes of praseodymium 120.955 u (Pr) to 158.955 u (Pr). The primary decay mode before the stable isotope, Pr, is electron capture and the mode after is beta decay. The primary decay products before Pr are element 58 (cerium) isotopes and the primary products after are element 60 (neodymium) isotopes. Isotopes of praseodymium Naturally occurring praseodymium (Pr) is composed of one stable isotope, Pr. Thirty-eight radioisotopes have been characterized with the most stable being Pr, with a half-life of 13.57 days and Pr, with a half-life of 19.12 hours. All of the remaining radioactive isotopes have half-lives that are less than 5.985 hours

neg: Isotopes of vanadium and none of the heavier, have unknown half-lives. In 4 isotopes, metastable excited states were found (including 2 metastable states for V), which adds up to 5 meta states. The primary decay mode before the most abundant stable isotope V is electron capture. The next most common mode is beta decay. The primary decay products before V are element 22 (titanium) isotopes and the primary products after are element 24 (chromium) isotopes. Isotopes of vanadium Naturally occurring vanadium (V) is composed of one stable isotope V and one radioactive isotope V with a half-life of 1.5×10 years. 24 artificial radioisotopes

neg: Isotopes of gadolinium majority of these have half-lives less than 24.6 seconds. Gadolinium isotopes have 10 metastable isomers, with the most stable being Gd (t=110 seconds), Gd (t=85 seconds) and Gd (t=24.5 seconds). The primary decay mode at atomic weights lower than the most abundant stable isotope, Gd, is electron capture, and the primary mode at higher atomic weights is beta decay. The primary decay products for isotopes of weights lower than Gd are the element Eu (europium) isotopes and the primary products at higher weights are the element Tb (terbium) isotopes. Gadolinium-153 has a half-life of 240.4±10 days and emits gamma radiation

neg: Isotopes of plutonium While it created delays and headaches during the Manhattan Project because of the need to develop implosion technology, those very same difficulties are currently a barrier to nuclear proliferation. Implosion devices are also inherently more efficient and less prone to accidental detonation than are gun-type weapons. Isotopes of plutonium Plutonium (Pu) is an artificial element, except for trace quantities resulting from neutron capture by uranium, and thus a standard atomic weight cannot be given. Like all artificial elements, it has no stable isotopes. It was synthesized long before being found in nature, the first isotope synthesized being Pu in 1940.

neg: Isotope times the mass of protium. These mass differences also affect the behavior of their respective chemical bonds, by changing the center of gravity (reduced mass) of the atomic systems. However, for heavier elements the relative mass difference between isotopes is much less, so that the mass-difference effects on chemistry are usually negligible. (Heavy elements also have relatively more neutrons than lighter elements, so the ratio of the nuclear mass to the collective electronic mass is slightly greater.) Similarly, two molecules that differ only in the isotopes of their atoms (isotopologues) have identical electronic structure, and therefore almost indistinguishable physical and

neg: Isotope the mass of the electrons associated with the atom, the latter because the electron:nucleon ratio differs among isotopes. The mass number is a dimensionless quantity. The atomic mass, on the other hand, is measured using the atomic mass unit based on the mass of the carbon-12 atom. It is denoted with symbols "u" (for unified atomic mass unit) or "Da" (for dalton). The atomic masses of naturally occurring isotopes of an element determine the atomic mass of the element. When the element contains "N" isotopes, the expression below is applied for the average atomic mass formula_1: formula_2 where "m", "m",

neg: Erbium 4 minutes. This element also has 13 meta states, with the most stable being with a half-life of . The isotopes of erbium range in atomic weight from () to (). The primary decay mode before the most abundant stable isotope, , is electron capture, and the primary mode after is beta decay. The primary decay products before are element 67 (holmium) isotopes, and the primary products after are element 69 (thulium) isotopes. Erbium (for Ytterby, a village in Sweden) was discovered by Carl Gustaf Mosander in 1843. Mosander was working with a sample of what was thought to be

neg: Chemical element naturally produced in nucleogenic reactions, or in cosmogenic processes, such as cosmic ray spallation. New atoms are also naturally produced on Earth as radiogenic daughter isotopes of ongoing radioactive decay processes such as alpha decay, beta decay, spontaneous fission, cluster decay, and other rarer modes of decay. Of the 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one stable isotope (except for technetium, element 43 and promethium, element 61, which have no stable isotopes). Isotopes considered stable are those for which no radioactive decay has yet been observed. Elements with atomic numbers 83

neg: Boron CBH. Characteristically such compounds contain boron with coordination numbers greater than four. Boron has two naturally occurring and stable isotopes, B (80.1%) and B (19.9%). The mass difference results in a wide range of δB values, which are defined as a fractional difference between the B and B and traditionally expressed in parts per thousand, in natural waters ranging from −16 to +59. There are 13 known isotopes of boron, the shortest-lived isotope is B which decays through proton emission and alpha decay. It has a half-life of 3.5×10 s. Isotopic fractionation of boron is controlled by the exchange reactions

neg: Silver days) and Ag ("t" = 8.28 days). All of the remaining radioactive isotopes have half-lives of less than an hour, and the majority of these have half-lives of less than three minutes. Isotopes of silver range in relative atomic mass from 92.950 u (Ag) to 129.950 u (Ag); the primary decay mode before the most abundant stable isotope, Ag, is electron capture and the primary mode after is beta decay. The primary decay products before Ag are palladium (element 46) isotopes, and the primary products after are cadmium (element 48) isotopes. The palladium isotope Pd decays by beta emission to

neg: Cobalt (Co). The primary decay mode for isotopes with atomic mass unit values less than that of the most abundant stable isotope, Co, is electron capture and the primary mode of decay in isotopes with atomic mass greater than 59 atomic mass units is beta decay. The primary decay products below Co are element 26 (iron) isotopes; above that the decay products are element 28 (nickel) isotopes. Cobalt compounds have been used for centuries to impart a rich blue color to glass, glazes, and ceramics. Cobalt has been detected in Egyptian sculpture, Persian jewelry from the third millennium BC, in the

neg: Environmental isotopes 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. formula_1 ‰ These variations in isotopes can occur through many types of fractionation. They are generally classified as mass independent fractionation and mass dependent fractionation. An example of a mass independent process is the fractionation of oxygen

neg: Atomic form factor of formula_21. Since the interaction is nuclear, each isotope has a different scattering amplitude. This Fourier transform is scaled by the amplitude of the spherical wave, which has dimensions of length. Hence, the amplitude of scattering that characterizes the interaction of a neutron with a given isotope is termed the scattering length, "b". Neutron scattering lengths vary erratically between neighbouring elements in the periodic table and between isotopes of the same element. They may only be determined experimentally, since the theory of nuclear forces is not adequate to calculate or predict "b" from other properties of the nucleus. Although neutral,

neg: Isotopes of tennessine which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given. DNS = Di-nuclear system; σ = cross section Theoretical calculations in a quantum tunneling model with mass estimates from a macroscopic-microscopic model predict the alpha-decay half-lives of isotopes of tennessine (namely, Ts) to be around 0.1–40 ms. Isotopes of tennessine Tennessine (Ts) is the most-recently synthesized synthetic element, and much of the data is hypothetical. As for any synthetic element, a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The

neg: Isotopes of technetium Isotopes of technetium Technetium (Tc) is the first of the two elements lighter than bismuth that have no non-radioactive isotopes; the other such element is promethium. It is primarily artificial, with only trace quantities (About 16 thousand metric tonnes) existing in nature produced by spontaneous fission or neutron capture by molybdenum. The first isotopes to be synthesized were Tc and Tc in 1936, the first artificial element to be produced. The most stable radioisotopes are Tc (half-life of 4.21 million years), Tc (half-life: 4.2 million years) and Tc (half-life: 211,100 years). Thirty-three other radioisotopes have been characterized with atomic masses

neg: Isotopes of silver Ag ("t" 249.79 days) and Ag ("t" 8.28 days). Isotopes of silver range in atomic weight from 92.950 u (Ag) to 129.950 u (Ag). The primary decay mode before the most abundant stable isotope, Ag, is electron capture and the primary mode after is beta decay. The primary decay products before Ag are palladium (element 46) isotopes and the primary products after are cadmium (element 48) isotopes. The palladium isotope Pd decays by beta emission to Ag with a half-life of 6.5 million years. Iron meteorites are the only objects with a high enough palladium/silver ratio to yield measurable variations

neg: Nuclear transmutation the environment. They are also mixed with larger quantities of other isotopes of the same element. Nuclear transmutation Nuclear transmutation is the conversion of one chemical element or an isotope into another chemical element. Because any element (or isotope of one) is defined by its number of protons (and neutrons) in its atoms, i.e. in the atomic nucleus, nuclear transmutation occurs in any process where the number of protons or neutrons in the nucleus is changed. A transmutation can be achieved either by nuclear reactions (in which an outside particle reacts with a nucleus) or by radioactive decay, where no

neg: Tennessine the bond a partially ionic character. Tennessine Tennessine is a synthetic chemical element with symbol Ts and atomic number 117. It is the second-heaviest known element and the penultimate element of the 7th period of the periodic table. The discovery of tennessine was officially announced in Dubna, Russia, by a Russian–American collaboration in April 2010, which makes it the most recently discovered element . One of its daughter isotopes was created directly in 2011, partially confirming the results of the experiment. The experiment itself was repeated successfully by the same collaboration in 2012 and by a joint German–American team in

neg: Tennessine Tennessine Tennessine is a synthetic chemical element with symbol Ts and atomic number 117. It is the second-heaviest known element and the penultimate element of the 7th period of the periodic table. The discovery of tennessine was officially announced in Dubna, Russia, by a Russian–American collaboration in April 2010, which makes it the most recently discovered element . One of its daughter isotopes was created directly in 2011, partially confirming the results of the experiment. The experiment itself was repeated successfully by the same collaboration in 2012 and by a joint German–American team in May 2014. In December 2015, the

neg: Spectral method Spectral method Spectral methods are a class of techniques used in applied mathematics and scientific computing to numerically solve certain differential equations, potentially involving the use of the fast Fourier transform. The idea is to write the solution of the differential equation as a sum of certain "basis functions" (for example, as a Fourier series which is a sum of sinusoids) and then to choose the coefficients in the sum in order to satisfy the differential equation as well as possible. Spectral methods and finite element methods are closely related and built on the same ideas; the main difference between

neg: Nihonium Lr, as in the Bh chains observed at LBNL. In June 2006, the JINR–LLNL collaboration claimed to have synthesised a new isotope of element 113 directly by bombarding a neptunium-237 target with accelerated calcium-48 nuclei: Two atoms of 113 were detected. The aim of this experiment had been to synthesise the isotopes 113 and 113 that would fill in the gap between isotopes produced via hot fusion (113 and 113) and cold fusion (113). After five alpha decays, these nuclides would reach known isotopes of lawrencium, assuming that the decay chains were not terminated prematurely by spontaneous fission. The first

neg: Isotopes of beryllium with 4 protons and 6 neutrons by the very large mismatch in proton/neutron ratio for such a light element. Nevertheless, this isotope, , has a half-life of 1.39 million years, which indicates unusual stability for a light isotope with such a large neutron/proton imbalance. Still other possible beryllium isotopes have even more severe mismatches in neutron and proton number, and thus are even less stable. Most in the universe is thought to be formed by cosmic ray nucleosynthesis from cosmic ray spallation in the period between the Big Bang and the formation of the solar system. The isotopes , with

neg: Heavy water deuterium, prokaryotic organisms such as bacteria, which do not have the mitotic problems induced by deuterium, may be grown and propagated in fully deuterated conditions, resulting in replacement of all hydrogen atoms in the bacterial proteins and DNA with the deuterium isotope. Full replacement with heavy atom isotopes can be accomplished in higher organisms with other non-radioactive heavy isotopes (such as carbon-13, nitrogen-15, and oxygen-18), but this cannot be done for the stable heavy isotope of hydrogen. This is a consequence of the relative difference in nuclear mass between the isotopes of hydrogen that is the greatest in all elements.

neg: Amateur radio licensing in the United States 1987, the only difference between the requirements for Technician and General licenses was the Morse telegraphy test, which was five words per minute (wpm) for Technician and 13 wpm for General. The written test, then called element 3, was the same for both classes. In 1987, a number of changes, later called the "Novice Enhancement," were introduced. Among them, element 3 was split into two new exams, element 3A, which covered VHF theory and 3B, which covered HF theory. Element 3A became a requirement for the Technician class and element 3B became a requirement for General. Both classes also required

neg: Radiosity (computer graphics) power can be distributed by generating a set of rays from the radiating element in the same way, and spreading the power to be distributed equally between each element a ray hits. This is essentially the same distribution that a path-tracing program would sample in tracing back one diffuse reflection step; or that a bidirectional ray tracing program would sample to achieve one forward diffuse reflection step when light source mapping forwards. The sampling approach therefore to some extent represents a convergence between the two techniques, the key difference remaining that the radiosity technique aims to build up a sufficiently

neg: Alkali metal can be only a single beta-stable nuclide, since there is not a difference in binding energy between even–odd and odd–even comparable to that between even–even and odd–odd, leaving other nuclides of the same mass number (isobars) free to beta decay toward the lowest-mass nuclide. An effect of the instability of an odd number of either type of nucleons is that odd-numbered elements, such as the alkali metals, tend to have fewer stable isotopes than even-numbered elements. Of the 26 monoisotopic elements that have only a single stable isotope, all but one have an odd atomic number and all but one

neg: Principal quantum number same "n" value are often referred to as electron shells or energy levels. The minimum energy exchanged during any wave-matter interaction is the product of the wave frequency multiplied by Planck's constant. This causes the wave to display particle-like packets of energy called quanta. The difference between energy levels that have different "n" determine the emission spectrum of the element. In the notation of the periodic table, the main shells of electrons are labeled: based on the principal quantum number. The principal quantum number is related to the radial quantum number, "n", by: where "ℓ" is the azimuthal quantum number

neg: Crystal Beach Cyclone was between the spiral's exit and the figure 8 element). All three were very similar in their design, following the same basic layout. The main difference in the design was that the spiral on the Cyclone at Palisades was even tighter than the two preceding coasters because of the extremely limited space in the park. The ride ran one or two trains consisting of three or five four-passenger cars depending on crowds. Later, the trains would be permanently reduced to three cars to keep forces on the structure lower. Ride time was around 40 seconds, discounting station to top of

neg: The Godfather (2006 video game) not be the same game as the PlayStation 2, Xbox and Windows versions. At a press event on July 13, 2006, EA debuted "Mob Wars". The main difference between this version and the others is that "Mob Wars" does not feature an open-world environment in which the player is free to move around and extort whatever businesses they wish. Instead, the game features two distinct game modes; "Story Mode" and "Mob Wars." The "Mob Wars" mode replaces the open world element from the other versions of the game and is played from a top down view in which the player

neg: Subatomic particle the prerequisite basics of Newtonian mechanics, a series of statements and equations in "Philosophiae Naturalis Principia Mathematica", originally published in 1687. The negatively charged electron has a mass equal to of that of a hydrogen atom. The remainder of the hydrogen atom's mass comes from the positively charged proton. The atomic number of an element is the number of protons in its nucleus. Neutrons are neutral particles having a mass slightly greater than that of the proton. Different isotopes of the same element contain the same number of protons but differing numbers of neutrons. The mass number of an isotope

neg: Applied element method polymers (GFRP) walls under blast loads. In AEM, the structure is divided virtually and modeled as an assemblage of relatively small elements. The elements are then connected through a set of normal and shear springs located at contact points distributed along the element faces. Normal and shear springs are responsible for the transfer of normal and shear stresses from one element to the next. The modeling of objects in AEM is very similar to modeling objects in FEM. Each object is divided into a series of elements connected and forming a mesh. The main difference between AEM and FEM, however,

neg: Chemical element their atomic nucleus; so the atomic number of carbon is 6. Carbon atoms may have different numbers of neutrons; atoms of the same element having different numbers of neutrons are known as isotopes of the element. The number of protons in the atomic nucleus also determines its electric charge, which in turn determines the number of electrons of the atom in its non-ionized state. The electrons are placed into atomic orbitals that determine the atom's various chemical properties. The number of neutrons in a nucleus usually has very little effect on an element's chemical properties (except in the case of

neg: Period 6 element away rapidly, so much less is known about this element than its upper neighbors in the periodic table. Earlier studies have shown this element follows periodic trends, being the heaviest known halogen, with melting and boiling points being higher than those of lighter halogens. Until recently most of the chemical characteristics of astatine were inferred from comparison with other elements; however, important studies have already been done. The main difference between astatine and iodine is that the HAt molecule is chemically a hydride rather than a halide; however, in a fashion similar to the lighter halogens, it is known to

neg: Marra language the morphemes is strictly set. Within the clause, however, the order of the NPs, verb complexes, and adverbs is free. The first element is typically considered to be the most important element. If the first element is not a verb complex, the main verb complex commonly but not always assumes the second position; there appears to be no difference in meaning between those sentences that place the verb complex in the second position and those that do not. Subordinated clauses are typically marked by a particle or conjunction such as "bigana" “because” or "waninggayani" “after that.” If, however, the clause

neg: Isotope hydrology Isotope hydrology Isotope hydrology is a field of hydrology that uses isotopic dating to estimate the age and origins of water and of movement within the hydrologic cycle. The techniques are used for water-use policy, mapping aquifers, conserving water supplies, and controlling pollution. It replaces or supplements past methods of measuring rain, river levels and other bodies of water over many decades. Water molecules carry unique fingerprints, based in part on differing proportions of the oxygen and hydrogen isotopes that constitute all water. Isotopes are forms of the same element that have variable numbers of neutrons in their nuclei. Air,

neg: Isotope show that the two isotopic masses are very close to the integers 20 and 22, and that neither is equal to the known molar mass (20.2) of neon gas. This is an example of Aston's whole number rule for isotopic masses, which states that large deviations of elemental molar masses from integers are primarily due to the fact that the element is a mixture of isotopes. Aston similarly showed that the molar mass of chlorine (35.45) is a weighted average of the almost integral masses for the two isotopes Cl and Cl. A neutral atom has the same number of

neg: Atomic number and the mass defect of nucleon binding is always small compared to the nucleon mass, the atomic mass of any atom, when expressed in unified atomic mass units (making a quantity called the "relative isotopic mass"), is within 1% of the whole number "A". Atoms with the same atomic number "Z" but different neutron numbers "N", and hence different atomic masses, 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)

neg: Radium this scheme, Ra was named actinium X (AcX), Ra thorium X (ThX), Ra radium (Ra), and Ra mesothorium 1 (MsTh). When it was realized that all of these are isotopes of the same element, many of these names fell out of use, and "radium" came to refer to all isotopes, not just Ra. Some of radium-226's decay products received historical names including "radium", ranging from radium A to radium G, with the letter indicating approximately how far they were down the chain from their parent Ra. Ra is the most stable isotope of radium and is the last isotope in

neg: Hydrogen isotope biogeochemistry same number of protons with varying numbers of neutrons. The element hydrogen has three naturally occurring isotopes, H, H and H, which are sometimes referred to as protium (H), deuterium (D) and tritium (T), respectively. Both H and H are stable indefinitely, while H is unstable and undergoes beta decay to form He. While there are some important applications of H in geochemistry (such as its use as an ocean circulation tracer) these will not be discussed further here. The study of stable isotope biogeochemistry involves the description of the relative abundances of various isotopes in a certain chemical pool,

neg: Isotope separation nuclear weapons. Plutonium-based weapons use plutonium produced in a nuclear reactor, which must be operated in such a way as to produce plutonium already of suitable isotopic mix or "grade". While different chemical elements can be purified through chemical processes, isotopes of the same element have nearly identical chemical properties, which makes this type of separation impractical, except for separation of deuterium. There are three types of isotope separation techniques: The third type of separation is still experimental; practical separation techniques all depend in some way on the atomic mass. It is therefore generally easier to separate isotopes with a

neg: Period 5 element and symbol Tc. It is the lowest atomic number element without any stable isotopes; every form of it is radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature. Naturally occurring technetium occurs as a spontaneous fission product in uranium ore or by neutron capture in molybdenum ores. The chemical properties of this silvery gray, crystalline transition metal are intermediate between rhenium and manganese. Many of technetium's properties were predicted by Dmitri Mendeleev before the element was discovered. Mendeleev noted a gap in his periodic table and gave the undiscovered element the provisional name "ekamanganese"

neg: Isotope (counting as stable), and 26 elements have only a single stable isotope (of these, 19 are so-called mononuclidic elements, having a single primordial stable isotope that dominates and fixes the atomic weight of the natural element to high precision; 3 radioactive mononuclidic elements occur as well). In total, there are 253 nuclides that have not been observed to decay. For the 80 elements that have one or more stable isotopes, the average number of stable isotopes is 253/80 = 3.1625 isotopes per element. The proton:neutron ratio is not the only factor affecting nuclear stability. It depends also on evenness or