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Radioactive Radioactive 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. A material containing such unstable nuclei is considered radioactive. Certain highly excited shortlived nuclear states can decay through neutron emission, or more rarely, proton emission. Radioactive Radioactive decay is a stochastic (i.e. random) process at the level of single atoms, in that, according to quantum theory, it is impossible to predict when a particular atom will decay,[1][2][3] regardless of how long the atom has existed [...More...] 


Neutron Excess The neutron number, symbol N, is the number of neutrons in a nuclide. Atomic number Atomic number (proton number) plus neutron number equals mass number: Z+N=A. The difference between the neutron number and the atomic number is known as the neutron excess: D = N  Z = A  2Z. Neutron Neutron number is rarely written explicitly in nuclide symbol notation, but appears as a subscript to the right of the element symbol. In order of increasing explicitness and decreasing frequency of usage:Element CIsotope/Nuclide 14CWith atomic number 14 6CWith neutron number 14 6C 8Nuclides that have the same neutron number but a different proton number are called isotones. This word was formed by replacing the p in isotope with n for neutron. Nuclides that have the same mass number are called isobars [...More...] 


Atomic Number The atomic number or proton number (symbol Z) of a chemical element is the number of protons found in the nucleus of an atom. It is identical to the charge number of the nucleus. The atomic number uniquely identifies a chemical element. In an uncharged atom, the atomic number is also equal to the number of electrons. The sum of the atomic number Z and the number of neutrons, N, gives the mass number A of an atom. Since protons and neutrons have approximately the same mass (and the mass of the electrons is negligible for many purposes) 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 [...More...] 


Neutron Number The neutron number, symbol N, is the number of neutrons in a nuclide. Atomic number Atomic number (proton number) plus neutron number equals mass number: Z+N=A. The difference between the neutron number and the atomic number is known as the neutron excess: D = N  Z = A  2Z. Neutron Neutron number is rarely written explicitly in nuclide symbol notation, but appears as a subscript to the right of the element symbol. In order of increasing explicitness and decreasing frequency of usage:Element CIsotope/Nuclide 14CWith atomic number 14 6CWith neutron number 14 6C 8Nuclides that have the same neutron number but a different proton number are called isotones. This word was formed by replacing the p in isotope with n for neutron. Nuclides that have the same mass number are called isobars [...More...] 


Particle Decay Particle decay Particle decay is the spontaneous process of one unstable subatomic particle transforming into multiple other particles. The particles created in this process (the final state) must each be less massive than the original, although the total invariant mass of the system must be conserved. A particle is unstable if there is at least one allowed final state that it can decay into. Unstable particles will often have multiple ways of decaying, each with its own associated probability [...More...] 


Magic Number (physics) In nuclear physics, a magic number is a number of nucleons (either protons or neutrons, separately) such that they are arranged into complete shells within the atomic nucleus. The seven most widely recognized magic numbers as of 2007 are 2, 8, 20, 28, 50, 82, and 126 (sequence A018226 in the OEIS). For protons, this corresponds to the elements helium, oxygen, calcium, nickel, tin, lead and the hypothetical unbihexium, although 126 is so far only known to be a magic number for neutrons. Atomic nuclei consisting of such a magic number of nucleons have a higher average binding energy per nucleon than one would expect based upon predictions such as the semiempirical mass formula and are hence more stable against nuclear decay. The unusual stability of isotopes having magic numbers means that transuranium elements can be created with extremely large nuclei and yet not be subject to the extremely rapid radioactive decay normally associated with high atomic numbers [...More...] 


Semiempirical Mass Formula In nuclear physics, the semiempirical mass formula (SEMF) (sometimes also called Weizsäcker's formula, or the Bethe–Weizsäcker formula, or the Bethe–Weizsäcker mass formula to distinguish it from the Bethe–Weizsäcker process) is used to approximate the mass and various other properties of an atomic nucleus from its number of protons and neutrons. As the name suggests, it is based partly on theory and partly on empirical measurements. The theory is based on the liquid drop model proposed by George Gamow, which can account for most of the terms in the formula and gives rough estimates for the values of the coefficients [...More...] 


Halo Nucleus In nuclear physics, an atomic nucleus is called a halo nucleus or is said to have a nuclear halo when it has a core nucleus surrounded by a "halo" of orbiting protons or neutrons, which makes the radius of the nucleus appreciably larger than that predicted by the liquid drop model. Halo nuclei form at the extreme edges of the table of nuclides — the neutron drip line and proton drip line — and have short halflives, measured in milliseconds. These nuclei are studied shortly after their formation in an ion beam. Typically, an atomic nucleus is a tightly bound group of protons and neutrons. However, in some nuclides, there is an overabundance of one species of nucleon [...More...] 


Even And Odd Atomic Nuclei In nuclear physics, properties of a nucleus depend on evenness or oddness of its atomic number Z, neutron number N and, consequently, of their sum, the mass number A. Most notably, oddness of both Z and N tends to lower the nuclear binding energy, making odd nuclei, generally, less stable. This effect is not only experimentally observed, but is included to the semiempirical mass formula and explained by some other nuclear models, such as nuclear shell model. This remarkable difference of nuclear binding energy between neighbouring nuclei, especially of oddA isobars, has important consequences for beta decay. Also, the nuclear spin is integer for all evenA nuclei and noninteger (halfinteger) for all oddA nuclei.Even vs. odd mass number (A).Even Odd TotalStable 152 101 253Longlived 24 9 33All primordial 176 110 286The neutron–proton ratio is not the only factor affecting nuclear stability [...More...] 


Stable Isotope 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 isotope fractionation in nature [...More...] 


Mirror Nuclei Mirror nuclei Mirror nuclei are nuclei where the number of protons of element one (Z1) equals the number of neutrons of element two (N2) and the number of protons of element two (Z2) equals the number of neutrons in element one (N1), such that the mass number is the same (A = N1 + Z1 = N2 + Z2). As that Z1 = N2 and Z2 = N1, A = N1 + N2 = Z1 + Z2. By making the substitution Z1 = Z and Z2 = Z − 1, the mass number can be rewritten in the form 2Z  1. Examples of mirror nuclei:3H and 3He: Jπ = 1/2+ 14C and 14O: Jπ = 0+ 15N and 15O: Jπ = 1/2− 24Na and 24Al: Jπ = 4+ 24mNa and 24mAl: Jπ = 1+Pairs of mirror nuclei have the same spin and parity. If we constrain to odd number of nucleons (A=Z+N) then we find mirror nuclei that differ one another by exchanging a proton by a neutron [...More...] 


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 234 90Th and 238 92U 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 12 6C, 16 8O, and 14 7N. The daughter nuclide of an alpha decay is an isodiapher of the original nucleus [...More...] 


Isobar (nuclide) Isobars are atoms (nuclides) of different chemical elements that have the same number of nucleons. Correspondingly, isobars differ in atomic number (or number of protons) but have the same mass number. An example of a series of isobars would be 40S, 40Cl, 40Ar, 40K, and 40Ca. The nuclei of these nuclides all contain 40 nucleons; however, they contain varying numbers of protons and neutrons.[1] The term "isobars" (originally "isobares") for nuclides was suggested by Alfred Walter Stewart in 1918.[2] It is derived from the Greek word isos, meaning "equal" and baros, meaning "weight".[3]Contents1 Mass 2 Stability 3 See also 4 Bibliography 5 ReferencesMass[edit] The same mass number implies neither the same mass of nuclei, nor equal atomic masses of corresponding nuclides [...More...] 


Ab Initio Methods (nuclear Physics) In nuclear physics, ab initio methods seek to describe the atomic nucleus from the ground up by solving the nonrelativistic Schrödinger equation Schrödinger equation for all constituent nucleons and the forces between them. This is done either exactly for very light nuclei (up to four nucleons) or by employing certain wellcontrolled approximations for heavier nuclei. Ab initio methods constitute a more fundamental approach compared to e.g. the nuclear shell model. Recent progress has enabled ab initio treatment of heavier nuclei such as nickel.[1] A significant challenge in the ab initio treatment stems from the complexities of the internucleon interaction. The strong nuclear force is believed to emerge from the strong interaction described by quantum chromodynamics (QCD), but QCD is nonperturbative in the lowenergy regime relevant to nuclear physics [...More...] 


Interacting Boson Model The interacting boson model (IBM) is a model in nuclear physics in which nucleons (protons or neutrons) pair up, essentially acting as a single particle with boson properties, with integral spin of 0, 2 or 4. It is sometimes known as the Interacting boson approximation (IBA).[1]:7 The IBM1/IBMI model treats both types of nucleons the same and considers only pairs of nucleons coupled to total angular momentum 0 and 2, called respectively, s and d bosons. The IBM2/IBMII model treats protons and neutrons separately. Both models are restricted to nuclei with even numbers of protons and neutrons.[1]:9Regions of differently shaped nuclei, as predicted by the Interacting Boson [...More...] 


Isotone Two nuclides are isotones if they have the same neutron number N, but different proton number Z. For example, boron12 and carbon13 nuclei both contain 7 neutrons, and so are isotones. Similarly, 36S, 37Cl, 38Ar, 39K, and 40Ca nuclei are all isotones of 20 because they all contain 20 neutrons. Despite its similarity to the Greek for "same stretching", the term was formed by the German physicist K. Guggenheimer[1] by changing the "p" in "isotope" from "p" for "proton" to "n" for "neutron".[2] The largest numbers of observationally stable nuclides exist for isotones 50 (five: 86Kr, 88Sr, 89Y, 90Zr, 92Mo) and 82 (six: 138Ba, 139La, 140Ce, 141Pr, 142Nd, 144Sm). Neutron Neutron numbers for which there are no stable isotones are 19, 21, 35, 39, 45, 61, 89, 115, 123, and 127 or more [...More...] 
