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Beta Decay
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 . For example, beta decay of a neutron transforms it into a proton by the emission of an electron, or conversely a proton is converted into a neutron by the emission of a positron (positron emission ), thus changing the nuclide type. Neither the beta particle nor its associated neutrino exist within the nucleus prior to beta decay, but are created in the decay process. By this process, unstable atoms obtain a more stable ratio of protons to neutrons . The probability of a nuclide decaying due to beta and other forms of decay is determined by its binding energy . The binding energies of all existing nuclides form what is called the nuclear valley of stability . Beta decay
Beta decay
is a consequence of the weak force , which is characterized by relatively lengthy decay times
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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: ElementC Isotope/Nuclide 14 C With atomic number 14 6C With neutron number 14 6C 8 Nuclides 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 . Nuclides that have the same neutron excess are called isodiaphers
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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 ). 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 semi-empirical 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
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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 half-lives, 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 isotopes, there is an overabundance of one species of nucleon. In some of these cases, a nuclear core and a halo will form
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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: ElementC Isotope/Nuclide 14 C With atomic number 14 6C With neutron number 14 6C 8 Nuclides 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 . Nuclides that have the same neutron excess are called isodiaphers
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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
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Virtual Particle
In physics , a VIRTUAL PARTICLE is a transient fluctuation that exhibits some of the characteristics of an ordinary particle, but whose existence is limited by the uncertainty principle . The concept of virtual particles arises in perturbation theory of quantum field theory where interactions between ordinary particles are described in terms of exchanges of virtual particles. Any process involving virtual particles admits a schematic representation known as a Feynman diagram , in which virtual particles are represented by internal lines. Virtual particles do not necessarily carry the same mass as the corresponding real particle, although they always conserve energy and momentum. The longer the virtual particle exists, the closer its characteristics come to those of ordinary particles. They are important in the physics of many processes, including particle scattering and Casimir forces
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Decay Product
In nuclear physics , a DECAY PRODUCT (also known as a DAUGHTER PRODUCT, DAUGHTER ISOTOPE or DAUGHTER NUCLIDE) is the remaining nuclide left over from radioactive decay . Radioactive decay
Radioactive decay
often proceeds via a sequence of steps (decay chain )
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Proton
6973167262189800000♠1.672621898(21)×10−27 kg 7002938272081300000♠938.2720813(58) MeV/c2 7000100727646687900♠1.007276466879(91) u MEAN LIFETIME > 7036662709600000000♠2.1×1029 years (stable) ELECTRIC CHARGE 6981160217648700000♠+1 e 6981160217662079999♠1.6021766208(98)×10−19 C CHARGE RADIUS 6999875100000000000♠0.8751(61) fm ELECTRIC DIPOLE MOMENT < 6976540000000000000♠5.4×10−24 e⋅cm ELECTRIC POLARIZABILITY 6997119999999999999♠1.20(6)×10−3 fm3 MAGNETIC MOMENT 6974141060678730000♠1.4106067873(97)×10−26 J ⋅T −1 6997152103220530000♠1.5210322053(46)×10−3 μB 7000279284735079999♠2.7928473508(85) μN MAGNETIC POLARIZABILITY 6996190000000000000♠1.9(5)×10−4 fm3 SPIN 1/2 ISOSPIN 1/2 PARITY +1 CONDENSED I (J P ) = 1/2(1/2+)A PROTON is a subatomic particle , symbol p or p+ , with a positive electric charge of +1e elementary charge and mass slightly less than that of a neutron
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Atomic Nucleus
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 . After the discovery of the neutron in 1932, models for a nucleus composed of protons and neutrons were quickly developed by Dmitri Ivanenko and Werner Heisenberg . Almost all of the mass of an atom is located in the nucleus, with a very small contribution from the electron cloud . Protons and neutrons are bound together to form a nucleus by the nuclear force
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Mass Number
The MASS NUMBER (symbol A), 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: N=A−Z. 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 12 C , which has 6 protons and 6 neutrons
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Stable Isotope
The term STABLE ISOTOPE has a similar meaning 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. This field is termed stable isotope geochemistry
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Island Of Stability
In nuclear physics , the ISLAND OF STABILITY is the prediction that a set of heavy nuclides with a near magic number of protons and neutrons will temporarily reverse the trend of decreasing stability in elements heavier than uranium . Although predictions of the exact location differ somewhat, Klaus Blaum expects the island of stability to occur in the atomic mass region near the nuclide 300 120Ubn . Estimates about the amount of stability on the island are usually around a half-life of minutes or days, with some predictions expecting half-lives of millions of years. Although the nuclear shell model has existed since the 1960s, the existence of such superheavy, relatively stable nuclides has not been demonstrated
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W Boson
The W AND Z BOSONS are together known as the WEAK or more generally as the INTERMEDIATE VECTOR BOSONS . These elementary particles mediate the weak interaction ; the respective symbols are W+ , W− , and Z . The W bosons have either a positive or negative electric charge of 1 elementary charge and are each other's antiparticles . The Z boson is electrically neutral and is its own antiparticle . The three particles have a spin of 1. The W bosons have a magnetic moment, but the Z has none. All three of these particles are very short-lived, with a half-life of about 6975300000000000000♠3×10−25 s. Their experimental discovery was a triumph for what is now known as the Standard Model
Standard Model
of particle physics . The W bosons are named after the Weak force. The physicist Steven Weinberg named the additional particle the "Z particle", and later gave the explanation that it was the last additional particle needed by the model
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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. The term "isobars" (originally "isobares") for nuclides was suggested by Alfred Walter Stewart in 1918. It is derived from the Greek word isos, meaning "equal" and baros, meaning "weight". CONTENTS * 1 Mass * 2 Stability * 3 See also * 4 Bibliography * 5 References MASSThe same mass number implies neither the same mass of nuclei , nor equal atomic masses of corresponding nuclides
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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 . Interesting to observe is their binding energy which is mainly due to the strong interaction and also due to Coulomb interaction
Coulomb interaction

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