174 relations: Abundance of the chemical elements, Actinide, Alexander Fleck, 1st Baron Fleck, Alpha decay, Aluminium-26, Anode ray, Antimony, Atom, Atomic mass, Atomic nucleus, Atomic number, Beta decay, Big Bang, Binding energy, Biogenic substance, Bromine, Carbon, Carbon-12, Carbon-13, Carbon-14, Centers for Disease Control and Prevention, Chemical element, Chemical reaction, Chemistry, Chlorine, Chlorine-37, Cluster decay, CNO cycle, Copper, Cosmic ray, Cosmic ray spallation, Cosmogenic nuclide, Decay chain, Deuterium, Dimensionless quantity, Electron, Electron capture, Fissile material, Francis William Aston, Frederick Soddy, French Alternative Energies and Atomic Energy Commission, Gallium, Gamma ray, George Thomas Beilby, Geotraces, Girdler sulfide process, Ground state, Half-life, Helium-3, Helium-4, ..., Infrared, Infrared spectroscopy, Internal conversion, International Atomic Energy Agency, International Union of Pure and Applied Chemistry, Iridium, Isobar (nuclide), Isodiapher, Isomer, Isoscapes, Isotone, Isotope, Isotope analysis, Isotope dilution, Isotope separation, Isotopes of chlorine, Isotopes of hydrogen, Isotopes of radium, Isotopes of tantalum, Isotopes of uranium, Isotopic labeling, Isotopic signature, Isotopologue, Isotopomers, J. J. Thomson, John Dalton, Journal of Agricultural and Food Chemistry, Kazimierz Fajans, Kinetic isotope effect, Lawrence Berkeley National Laboratory, List of elements by stability of isotopes, List of nuclides, List of particles, Manhattan Project, Margaret Todd (doctor), Mars, Martian meteorite, Mass number, Mass spectrometry, Mössbauer spectroscopy, Metastability, Molecule, Mononuclidic element, National Institute of Standards and Technology, Neon, Neutron, Neutron capture, Neutron number, Neutron temperature, Neutron–proton ratio, Niobium, Nobel Prize in Chemistry, Nuclear binding energy, Nuclear fission, Nuclear force, Nuclear fusion, Nuclear isomer, Nuclear magnetic resonance, Nuclear medicine, Nuclear power, Nuclear reaction, Nuclear technology, Nuclear weapon, Nucleogenic, Nucleon, Nucleosynthesis, Nuclide, Parity (mathematics), Parity of zero, Periodic table, Photon, Physical cosmology, Planetary and Space Science, Plutonium, Plutonium-244, Potassium, Potassium-40, Primordial nuclide, Promethium, Protein, Proton, Proton decay, R-process, Radiation therapy, Radioactive decay, Radioactive displacement law of Fajans and Soddy, Radiocarbon dating, Radiochemistry, Radiogenic nuclide, Radiometric dating, Radionuclide, Radium, Radon, Reduced mass, Reference materials for stable isotope analysis, Resolution (mass spectrometry), S-process, Sector mass spectrometer, Silver, Solar System, Spin (physics), Spontaneous fission, Stable isotope labeling by amino acids in cell culture, Stable isotope ratio, Stable nuclide, Stellar nucleosynthesis, Subscript and superscript, Symbol (chemistry), Synonym, Table of nuclides, Table of nuclides (combined), Technetium, Thallium, Theodore William Richards, Tin, Triple-alpha process, Tritium, Unified atomic mass unit, United Nations, Uranium, Uranium-235, Uranium-238, Whole number rule, Year. Expand index (124 more) » « Shrink index
The abundance of the chemical elements is a measure of the occurrence of the chemical elements relative to all other elements in a given environment.
The actinide or actinoid (IUPAC nomenclature) series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium.
Alexander Fleck, 1st Baron Fleck KBE LLD FRS FRSE (11 November 1889 – 6 August 1968) was a British industrial chemist.
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into an atom with a mass number that is reduced by four and an atomic number that is reduced by two.
Aluminium-26, 26Al, is a radioactive isotope of the chemical element aluminium, decaying by either of the modes beta-plus or electron capture, both resulting in the stable nuclide magnesium-26.
An anode ray (also positive ray or canal ray) is a beam of positive ions that is created by certain types of gas-discharge tubes.
Antimony is a chemical element with symbol Sb (from stibium) and atomic number 51.
An atom is the smallest constituent unit of ordinary matter that has the properties of a chemical element.
The atomic mass (ma) is the mass of an atom.
The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 Geiger–Marsden gold foil experiment.
The atomic number or proton number (symbol Z) of a chemical element is the number of protons found in the nucleus of an atom.
In nuclear physics, beta decay (β-decay) is a type of radioactive decay in which a beta ray (fast energetic electron or positron) and a neutrino are emitted from an atomic nucleus.
The Big Bang theory is the prevailing cosmological model for the universe from the earliest known periods through its subsequent large-scale evolution.
Binding energy (also called separation energy) is the minimum energy required to disassemble a system of particles into separate parts.
A biogenic substance is a substance produced by life processes.
Bromine is a chemical element with symbol Br and atomic number 35.
Carbon (from carbo "coal") is a chemical element with symbol C and atomic number 6.
Carbon-12 is the more abundant of the two stable isotopes of carbon (Carbon-13 being the other), amounting to 98.93% of the element carbon; its abundance is due to the triple-alpha process by which it is created in stars.
Carbon-13 (13C) is a natural, stable isotope of carbon with a nucleus containing six protons and seven neutrons.
Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.
The Centers for Disease Control and Prevention (CDC) is the leading national public health institute of the United States.
A chemical element is a species of atoms having the same number of protons in their atomic nuclei (that is, the same atomic number, or Z).
A chemical reaction is a process that leads to the transformation of one set of chemical substances to another.
Chemistry is the scientific discipline involved with compounds composed of atoms, i.e. elements, and molecules, i.e. combinations of atoms: their composition, structure, properties, behavior and the changes they undergo during a reaction with other compounds.
Chlorine is a chemical element with symbol Cl and atomic number 17.
Chlorine-37, or, is one of the stable isotopes of chlorine, the other being chlorine-35.
Cluster decay, also named heavy particle radioactivity or heavy ion radioactivity, is a type of nuclear decay in which an atomic nucleus emits a small "cluster" of neutrons and protons, more than in an alpha particle, but less than a typical binary fission fragment.
The CNO cycle (for carbon–nitrogen–oxygen) is one of the two known sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton–proton chain reaction.
Copper is a chemical element with symbol Cu (from cuprum) and atomic number 29.
Cosmic rays are high-energy radiation, mainly originating outside the Solar System and even from distant galaxies.
Cosmic ray spallation is a naturally occurring nuclear reaction causing nucleosynthesis.
Cosmogenic nuclides (or cosmogenic isotopes) are rare nuclides (isotopes) created when a high-energy cosmic ray interacts with the nucleus of an in situ Solar System atom, causing nucleons (protons and neutrons) to be expelled from the atom (see cosmic ray spallation).
In nuclear science, the decay chain refers to a series of radioactive decays of different radioactive decay products as a sequential series of transformations.
Deuterium (or hydrogen-2, symbol or, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1).
In dimensional analysis, a dimensionless quantity is a quantity to which no physical dimension is assigned.
The electron is a subatomic particle, symbol or, whose electric charge is negative one elementary charge.
Electron capture (K-electron capture, also K-capture, or L-electron capture, L-capture) is a process in which the proton-rich nucleus of an electrically neutral atom absorbs an inner atomic electron, usually from the K or L electron shell.
In nuclear engineering, fissile material is material capable of sustaining a nuclear fission chain reaction.
Francis William Aston FRS (1 September 1877 – 20 November 1945) was an English chemist and physicist who won the 1922 Nobel Prize in Chemistry for his discovery, by means of his mass spectrograph, of isotopes, in a large number of non-radioactive elements, and for his enunciation of the whole number rule.
Frederick Soddy FRS (2 September 1877 – 22 September 1956) was an English radiochemist who explained, with Ernest Rutherford, that radioactivity is due to the transmutation of elements, now known to involve nuclear reactions.
The French Alternative Energies and Atomic Energy Commission or CEA (French: Commissariat à l'énergie atomique et aux énergies alternatives), is a French public government-funded research organisation in the areas of energy, defense and security, information technologies and health technologies.
Gallium is a chemical element with symbol Ga and atomic number 31.
A gamma ray or gamma radiation (symbol γ or \gamma), is penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei.
Sir George Thomas Beilby (17 November 1850 – 1 August 1924) was a British chemist.
GEOTRACES is an international research programme that aims to improve an understanding of biogeochemical cycles in the oceans.
The Girdler sulfide (GS) process, also known as the GeibSpevack (GS) process, is an industrial production method for filtering out of natural water the heavy water (deuterium oxide.
The ground state of a quantum mechanical system is its lowest-energy state; the energy of the ground state is known as the zero-point energy of the system.
Half-life (symbol t1⁄2) is the time required for a quantity to reduce to half its initial value.
Helium-3 (He-3, also written as 3He, see also helion) is a light, non-radioactive isotope of helium with two protons and one neutron (common helium having two protons and two neutrons).
Helium-4 is a non-radioactive isotope of the element helium.
Infrared radiation (IR) is electromagnetic radiation (EMR) with longer wavelengths than those of visible light, and is therefore generally invisible to the human eye (although IR at wavelengths up to 1050 nm from specially pulsed lasers can be seen by humans under certain conditions). It is sometimes called infrared light.
Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) involves the interaction of infrared radiation with matter.
Internal conversion is a radioactive decay process wherein an excited nucleus interacts electromagnetically with one of the orbital electrons of the atom.
The International Atomic Energy Agency (IAEA) is an international organization that seeks to promote the peaceful use of nuclear energy, and to inhibit its use for any military purpose, including nuclear weapons.
The International Union of Pure and Applied Chemistry (IUPAC) is an international federation of National Adhering Organizations that represents chemists in individual countries.
Iridium is a chemical element with symbol Ir and atomic number 77.
Isobars are atoms (nuclides) of different chemical elements that have the same number of nucleons.
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.
An isomer (from Greek ἰσομερής, isomerès; isos.
Isoscapes are spatially explicit predictions of elemental isotope ratios (δ) that are produced by executing process-level models of elemental isotope fractionation or distribution in a Geographic Information System (GIS).
Two nuclides are isotones if they have the same neutron number N, but different proton number Z. For example, boron-12 and carbon-13 nuclei both contain 7 neutrons, and so are isotones.
Isotopes are variants of a particular chemical element which differ in neutron number.
Isotope analysis is the identification of isotopic signature, the abundance of certain stable isotopes and chemical elements within organic and inorganic compounds.
Isotope dilution analysis is a method of determining the quantity of chemical substances.
Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes.
Chlorine (17Cl) has 24 isotopes with mass numbers ranging from 28Cl to 51Cl and 2 isomers (34mCl and 38mCl).
Hydrogen (1H) has three naturally occurring isotopes, sometimes denoted 1H, 2H, and 3H.
Radium (88Ra) has no stable or nearly stable isotopes, and thus a standard atomic weight cannot be given.
Natural tantalum (73Ta) consists of two stable isotopes: 181Ta (99.988%) and (0.012%).
Uranium (92U) is a naturally occurring radioactive element that has no stable isotopes but two primordial isotopes (uranium-238 and uranium-235) that have long half-life and are found in appreciable quantity in the Earth's crust, along with the decay product uranium-234.
Isotopic labeling (or isotopic labelling) is a technique used to track the passage of an isotope (an atom with a detectable variation) through a reaction, metabolic pathway, or cell.
An isotopic signature (also isotopic fingerprint) is a ratio of non-radiogenic 'stable isotopes', stable radiogenic isotopes, or unstable radioactive isotopes of particular elements in an investigated material.
Isotopologues are molecules that differ only in their isotopic composition.
Isotopomers or isotopic isomers are isomers with isotopic atoms, having the same number of each isotope of each element but differing in their positions.
Sir Joseph John Thomson (18 December 1856 – 30 August 1940) was an English physicist and Nobel Laureate in Physics, credited with the discovery and identification of the electron; and with the discovery of the first subatomic particle.
John Dalton FRS (6 September 1766 – 27 July 1844) was an English chemist, physicist, and meteorologist.
The Journal of Agricultural and Food Chemistry is a weekly peer-reviewed scientific journal established in 1953 by the American Chemical Society.
Kazimierz Fajans (Kasimir Fajans in many American publications; 27 May 1887 – 18 May 1975) was a Polish American physical chemist of Polish-Jewish origin, a pioneer in the science of radioactivity and the discoverer of chemical element protactinium.
The kinetic isotope effect (KIE) is the change in the reaction rate of a chemical reaction when one of the atoms in the reactants is replaced by one of its isotopes.
Lawrence Berkeley National Laboratory (LBNL), commonly referred to as Berkeley Lab, is a United States national laboratory located in the Berkeley Hills near Berkeley, California that conducts scientific research on behalf of the United States Department of Energy (DOE).
Atomic nuclei consist of protons and neutrons, which attract each other through the nuclear force, while protons repel each other via the electric force due to their positive charge.
This list of nuclides shows observed nuclides that either are stable or, if radioactive, have half-lives longer than one hour.
This article includes a list of the different types of atomic- and sub-atomic particles found or hypothesized to exist in the whole of the universe categorized by type.
The Manhattan Project was a research and development undertaking during World War II that produced the first nuclear weapons.
Margaret Georgina Todd (23 April 1859 – 3 September 1918) was a Scottish doctor and writer.
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury.
A Martian meteorite is a rock that formed on the planet Mars and was then ejected from Mars by the impact of an asteroid or comet, and finally landed on the Earth.
The mass number (symbol A, from the German word Atomgewichte (atomic weight), also called atomic mass number or nucleon number, is the total number of protons and neutrons (together known as nucleons) in an atomic nucleus. It determines the atomic mass of atoms. Because protons and neutrons both are baryons, the mass number A is identical with the baryon number B as of the nucleus as of the whole atom or ion. The mass number is different for each different isotope of a chemical element. This is not the same as the atomic number (Z) which denotes the number of protons in a nucleus, and thus uniquely identifies an element. Hence, the difference between the mass number and the atomic number gives the number of neutrons (N) in a given nucleus:. The mass number is written either after the element name or as a superscript to the left of an element's symbol. For example, the most common isotope of carbon is carbon-12, or, which has 6 protons and 6 neutrons. The full isotope symbol would also have the atomic number (Z) as a subscript to the left of the element symbol directly below the mass number:. This is technically redundant, as each element is defined by its atomic number, so it is often omitted.
Mass spectrometry (MS) is an analytical technique that ionizes chemical species and sorts the ions based on their mass-to-charge ratio.
Mössbauer spectroscopy is a spectroscopic technique based on the Mössbauer effect.
In physics, metastability is a stable state of a dynamical system other than the system's state of least energy.
A molecule is an electrically neutral group of two or more atoms held together by chemical bonds.
A mononuclidic element or monotopic element is one of the 22 chemical elements that is found naturally on Earth essentially as a single nuclide (which may, or may not, be a stable nuclide).
The National Institute of Standards and Technology (NIST) is one of the oldest physical science laboratories in the United States.
Neon is a chemical element with symbol Ne and atomic number 10.
Neutron capture is a nuclear reaction in which an atomic nucleus and one or more neutrons collide and merge to form a heavier nucleus.
The neutron number, symbol N, is the number of neutrons in a nuclide.
The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts.
The neutron–proton ratio (N/Z ratio or nuclear ratio) of an atomic nucleus is the ratio of its number of neutrons to its number of protons.
Niobium, formerly known as columbium, is a chemical element with symbol Nb (formerly Cb) and atomic number 41.
The Nobel Prize in Chemistry (Nobelpriset i kemi) is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry.
Nuclear binding energy is the minimum energy that would be required to disassemble the nucleus of an atom into its component parts.
In nuclear physics and nuclear chemistry, nuclear fission is either a nuclear reaction or a radioactive decay process in which the nucleus of an atom splits into smaller parts (lighter nuclei).
The nuclear force (or nucleon–nucleon interaction or residual strong force) is a force that acts between the protons and neutrons of atoms.
In nuclear physics, nuclear fusion is a reaction in which two or more atomic nuclei come close enough to form one or more different atomic nuclei and subatomic particles (neutrons or protons).
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons (protons or neutrons).
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a magnetic field absorb and re-emit electromagnetic radiation.
Nuclear medicine is a medical specialty involving the application of radioactive substances in the diagnosis and treatment of disease.
Nuclear power is the use of nuclear reactions that release nuclear energy to generate heat, which most frequently is then used in steam turbines to produce electricity in a nuclear power plant.
In nuclear physics and nuclear chemistry, a nuclear reaction is semantically considered to be the process in which two nuclei, or else a nucleus of an atom and a subatomic particle (such as a proton, neutron, or high energy electron) from outside the atom, collide to produce one or more nuclides that are different from the nuclide(s) that began the process.
Nuclear technology is technology that involves the nuclear reactions of atomic nuclei.
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or from a combination of fission and fusion reactions (thermonuclear bomb).
A nucleogenic isotope, or nuclide, is one that is produced by a natural terrestrial nuclear reaction, other than a reaction beginning with cosmic rays (the latter nuclides by convention are called by the different term cosmogenic).
In chemistry and physics, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus.
Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons.
A nuclide (from nucleus, also known as nuclear species) is an atomic species characterized by the specific constitution of its nucleus, i.e., by its number of protons Z, its number of neutrons N, and its nuclear energy state.
In mathematics, parity is the property of an integer's inclusion in one of two categories: even or odd.
Zero is an even number.
The periodic table is a tabular arrangement of the chemical elements, ordered by their atomic number, electron configuration, and recurring chemical properties, whose structure shows periodic trends.
The photon is a type of elementary particle, the quantum of the electromagnetic field including electromagnetic radiation such as light, and the force carrier for the electromagnetic force (even when static via virtual particles).
Physical cosmology is the study of the largest-scale structures and dynamics of the Universe and is concerned with fundamental questions about its origin, structure, evolution, and ultimate fate.
Planetary and Space Science, published 15 times per year, is a peer-reviewed scientific journal established in 1959.
Plutonium is a radioactive chemical element with symbol Pu and atomic number 94.
Plutonium-244 (244Pu) is an isotope of plutonium that has a half-life of 80 million years.
Potassium is a chemical element with symbol K (from Neo-Latin kalium) and atomic number 19.
Potassium-40 (40K) is a radioactive isotope of potassium which has a very long half-life of 1.251 years.
In geochemistry, geophysics and geonuclear physics, primordial nuclides, also known as primordial isotopes, are nuclides found on Earth that have existed in their current form since before Earth was formed.
Promethium is a chemical element with symbol Pm and atomic number 61.
Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues.
In particle physics, proton decay is a hypothetical form of radioactive decay in which the proton decays into lighter subatomic particles, such as a neutral pion and a positron.
The rapid neutron-capture process, or so-called r-process, is a set of nuclear reactions that in nuclear astrophysics is responsible for the creation (nucleosynthesis) of approximately half the abundances of the atomic nuclei heavier than iron, usually synthesizing the entire abundance of the two most neutron-rich stable isotopes of each heavy element.
Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is therapy using ionizing radiation, generally as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator.
Radioactive decay (also known as nuclear decay or radioactivity) is the process by which an unstable atomic nucleus loses energy (in terms of mass in its rest frame) by emitting radiation, such as an alpha particle, beta particle with neutrino or only a neutrino in the case of electron capture, gamma ray, or electron in the case of internal conversion.
The law of radioactive displacements, also known as Fajans and Soddy law, in radiochemistry and nuclear physics, is a rule governing the transmutation of elements during radioactive decay.
Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon.
Radiochemistry is the chemistry of radioactive materials, where radioactive isotopes of elements are used to study the properties and chemical reactions of non-radioactive isotopes (often within radiochemistry the absence of radioactivity leads to a substance being described as being inactive as the isotopes are stable).
A radiogenic nuclide is a nuclide that is produced by a process of radioactive decay.
Radiometric dating or radioactive dating is a technique used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed.
A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is an atom that has excess nuclear energy, making it unstable.
Radium is a chemical element with symbol Ra and atomic number 88.
Radon is a chemical element with symbol Rn and atomic number 86.
In physics, the reduced mass is the "effective" inertial mass appearing in the two-body problem of Newtonian mechanics.
Isotopic reference materials are compounds (solids, liquids, gasses) with well-defined isotopic compositions and are the ultimate sources of accuracy in mass spectrometric measurements of isotope ratios.
In mass spectrometry, resolution measures of the ability to distinguish two peaks of slightly different mass-to-charge ratios ΔM, in a mass spectrum.
The slow neutron-capture process or s-process is a series of reactions in nuclear astrophysics that occur in stars, particularly AGB stars.
A sector instrument is a general term for a class of mass spectrometer that uses a static electric or magnetic sector or some combination of the two (separately in space) as a mass analyzer.
Silver is a chemical element with symbol Ag (from the Latin argentum, derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47.
The Solar SystemCapitalization of the name varies.
In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles, composite particles (hadrons), and atomic nuclei.
Spontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements.
Stable Isotope Labeling by/with Amino acids in Cell culture (SILAC) is a technique based on mass spectrometry that detects differences in protein abundance among samples using non-radioactive isotopic labeling.
The term stable isotope has a meaning similar to stable nuclide, but is preferably used when speaking of nuclides of a specific element.
Stable nuclides are nuclides that are not radioactive and so (unlike radionuclides) do not spontaneously undergo radioactive decay.
Stellar nucleosynthesis is the theory explaining the creation (nucleosynthesis) of chemical elements by nuclear fusion reactions between atoms within the stars.
A subscript or superscript is a character (number, letter or symbol) that is (respectively) set slightly below or above the normal line of type.
In relation to the chemical elements, a symbol is a code for a chemical element.
A synonym is a word or phrase that means exactly or nearly the same as another word or phrase in the same language.
A table of nuclides or chart of nuclides is a two-dimensional graph in which one axis represents the number of neutrons and the other represents the number of protons in an atomic nucleus.
The various tables below (scroll down) show the known isotopes of the chemical elements.
Technetium is a chemical element with symbol Tc and atomic number 43.
Thallium is a chemical element with symbol Tl and atomic number 81.
Theodore William Richards (January 31, 1868 – April 2, 1928) was the first American scientist to receive the Nobel Prize in Chemistry, earning the award "in recognition of his exact determinations of the atomic weights of a large number of the chemical elements.".
Tin is a chemical element with the symbol Sn (from stannum) and atomic number 50.
The triple-alpha process is a set of nuclear fusion reactions by which three helium-4 nuclei (alpha particles) are transformed into carbon.
Tritium (or; symbol or, also known as hydrogen-3) is a radioactive isotope of hydrogen.
The unified atomic mass unit or dalton (symbol: u, or Da) is a standard unit of mass that quantifies mass on an atomic or molecular scale (atomic mass).
The United Nations (UN) is an intergovernmental organization tasked to promote international cooperation and to create and maintain international order.
Uranium is a chemical element with symbol U and atomic number 92.
Uranium-235 (235U) is an isotope of uranium making up about 0.72% of natural uranium.
Uranium-238 (238U or U-238) is the most common isotope of uranium found in nature, with a relative abundance of 99%.
The whole number rule states that the masses of the isotopes are whole number multiples of the mass of the hydrogen atom.
A year is the orbital period of the Earth moving in its orbit around the Sun.