Misplaced Pages

#722277

67-558: The chemical properties of an atom are mostly determined by the configuration of electrons that orbit the atom's heavy nucleus. The electron configuration is determined by the charge of the nucleus, which is determined by the number of protons, or atomic number . The number of neutrons is the neutron number . Neutrons do not affect the electron configuration. Atoms of a chemical element that differ only in neutron number are called isotopes . For example, carbon , with atomic number 6, has an abundant isotope carbon-12 with 6 neutrons and

134-490: A Cabibbo–Kobayashi–Maskawa matrix ) via the weak interaction . The decay of one of the neutron's down quarks into a lighter up quark can be achieved by the emission of a W boson . By this process, the Standard Model description of beta decay, the neutron decays into a proton (which contains one down and two up quarks), an electron, and an electron antineutrino . The decay of the proton to a neutron occurs similarly through

201-408: A nuclear chain reaction . These events and findings led to the first self-sustaining nuclear reactor ( Chicago Pile-1 , 1942) and the first nuclear weapon ( Trinity , 1945). Dedicated neutron sources like neutron generators , research reactors and spallation sources produce free neutrons for use in irradiation and in neutron scattering experiments. A free neutron spontaneously decays to

268-554: A "neutron". The name derives from the Latin root for neutralis (neuter) and the Greek suffix -on (a suffix used in the names of subatomic particles, i.e. electron and proton ). References to the word neutron in connection with the atom can be found in the literature as early as 1899, however. Throughout the 1920s, physicists assumed that the atomic nucleus was composed of protons and "nuclear electrons", but this raised obvious problems. It

335-400: A "radiative decay mode" of the neutron, the gamma ray may be thought of as resulting from an "internal bremsstrahlung " that arises from the electromagnetic interaction of the emitted beta particle with the proton. A smaller fraction (about four per million) of free neutrons decay in so-called "two-body (neutron) decays", in which a proton, electron and antineutrino are produced as usual, but

402-441: A bottle, while the "beam" method employs energetic neutrons in a particle beam. The measurements by the two methods have not been converging with time. The lifetime from the bottle method is presently 877.75 s which is 10 seconds below the value from the beam method of 887.7 s A small fraction (about one per thousand) of free neutrons decay with the same products, but add an extra particle in the form of an emitted gamma ray: Called

469-543: A deuteron is formed by a proton capturing a neutron (this is exothermic and happens with zero-energy neutrons). The small recoil kinetic energy ( E r d {\displaystyle E_{rd}} ) of the deuteron (about 0.06% of the total energy) must also be accounted for. The energy of the gamma ray can be measured to high precision by X-ray diffraction techniques, as was first done by Bell and Elliot in 1948. The best modern (1986) values for neutron mass by this technique are provided by Greene, et al. These give

536-426: A half-life of about 12.7 hours. This isotope has one unpaired proton and one unpaired neutron, so either the proton or the neutron can decay. This particular nuclide is almost equally likely to undergo proton decay (by positron emission , 18% or by electron capture , 43%; both forming Ni ) or neutron decay (by electron emission, 39%; forming Zn ). Within the theoretical framework of

603-417: A mass spectrometer, the mass of a neutron can be deduced by subtracting proton mass from deuteron mass, with the difference being the mass of the neutron plus the binding energy of deuterium (expressed as a positive emitted energy). The latter can be directly measured by measuring the energy ( B d {\displaystyle B_{d}} ) of the single 2.224 MeV gamma photon emitted when

670-411: A mean-square radius of about 0.8 × 10  m , or 0.8  fm , and it is a spin-½ fermion . The neutron has no measurable electric charge. With its positive electric charge, the proton is directly influenced by electric fields , whereas the neutron is unaffected by electric fields. The neutron has a magnetic moment , however, so it is influenced by magnetic fields . The specific properties of

737-419: A negative value, because its orientation is opposite to the neutron's spin. The magnetic moment of the neutron is an indication of its quark substructure and internal charge distribution. In the quark model for hadrons , the neutron is composed of one up quark (charge +2/3  e ) and two down quarks (charge −1/3  e ). The magnetic moment of the neutron can be modeled as a sum of the magnetic moments of

SECTION 10

#1732851412723

804-544: A neutron mass of: The value for the neutron mass in MeV is less accurately known, due to less accuracy in the known conversion of Da to MeV/ c : Another method to determine the mass of a neutron starts from the beta decay of the neutron, when the momenta of the resulting proton and electron are measured. The neutron is a spin  ⁠ 1 / 2 ⁠ particle, that is, it is a fermion with intrinsic angular momentum equal to ⁠ 1 / 2 ⁠   ħ , where ħ

871-477: A nucleus behave similarly and can exchange their identities by similar reactions. These reactions are a form of radioactive decay known as beta decay . Beta decay, in which neutrons decay to protons, or vice versa, is governed by the weak force , and it requires the emission or absorption of electrons and neutrinos, or their antiparticles. The neutron and proton decay reactions are: where p , e , and ν e denote

938-460: A pair of protons, one with spin up, another with spin down. When all available proton states are filled, the Pauli exclusion principle disallows the decay of a neutron to a proton. The situation is similar to electrons of an atom, where electrons that occupy distinct atomic orbitals are prevented by the exclusion principle from decaying to lower, already-occupied, energy states. The stability of matter

1005-464: A proton and an electron bound in some way. Electrons were assumed to reside within the nucleus because it was known that beta radiation consisted of electrons emitted from the nucleus. About the time Rutherford suggested the neutral proton-electron composite, several other publications appeared making similar suggestions, and in 1921 the American chemist W. D. Harkins first named the hypothetical particle

1072-423: A proton, an electron , and an antineutrino , with a mean lifetime of about 15 minutes. Free neutrons do not directly ionize atoms, but they do indirectly cause ionizing radiation , so they can be a biological hazard, depending on dose. A small natural "neutron background" flux of free neutrons exists on Earth, caused by cosmic ray showers , and by the natural radioactivity of spontaneously fissionable elements in

1139-419: A rare isotope carbon-13 with 7 neutrons. Some elements occur in nature with only one stable isotope , such as fluorine . Other elements occur with many stable isotopes, such as tin with ten stable isotopes, or with no stable isotope, such as technetium . The properties of an atomic nucleus depend on both atomic and neutron numbers. With their positive charge, the protons within the nucleus are repelled by

1206-421: A spin  ⁠ 1 / 2 ⁠ particle. As a fermion, the neutron is subject to the Pauli exclusion principle ; two neutrons cannot have the same quantum numbers. This is the source of the degeneracy pressure which counteracts gravity in neutron stars and prevents them from forming black holes. Even though the neutron is a neutral particle, the magnetic moment of a neutron is not zero. The neutron

1273-413: A substance goes under a chemical reaction, the properties will change drastically, resulting in chemical change . However, a catalytic property would also be a chemical property. Chemical properties can be contrasted with physical properties , which can be discerned without changing the substance's structure. However, for many properties within the scope of physical chemistry , and other disciplines at

1340-408: Is a consequence of these constraints. The decay of a neutron within a nuclide is illustrated by the decay of the carbon isotope carbon-14 , which has 6 protons and 8 neutrons. With its excess of neutrons, this isotope decays by beta decay to nitrogen-14 (7 protons, 7 neutrons), a process with a half-life of about 5,730 years . Nitrogen-14 is stable. "Beta decay" reactions can also occur by

1407-600: Is a stable nuclide and a primordial radionuclide are 27 ( V), 65 ( Cd), 81 ( La), 84 ( Nd), 85 ( Sm), 86 ( Sm), 105 ( Lu), and 126 ( Bi). Neutron numbers for which there are two primordial radionuclides are 88 ( Eu and Gd) and 112 ( Re and Pt). The neutron numbers which have only one stable nuclide (compare: monoisotopic element for the proton numbers ) are: 0, 2, 3, 4, 9, 11, 13, 15, 17, 23, 25, 27, 29, 31, 33, 37, 41, 43, 47, 49, 51, 53, 57, 59, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 84, 85, 86, 87, 91, 93, 95, 97, 99, 101, 103, 105, 109, 111, 113, 117, 119, 121, 125, 126, and

SECTION 20

#1732851412723

1474-413: Is any of a material's properties that becomes evident during, or after, a chemical reaction ; that is, any attribute that can be established only by changing a substance's chemical identity . Simply speaking, chemical properties cannot be determined just by viewing or touching the substance; the substance's internal structure must be affected greatly for its chemical properties to be investigated. When

1541-431: Is approximately ten million times that from an equivalent mass of a conventional chemical explosive . Ultimately, the ability of the nuclear force to store energy arising from the electromagnetic repulsion of nuclear components is the basis for most of the energy that makes nuclear reactors or bombs possible; most of the energy released from fission is the kinetic energy of the fission fragments. Neutrons and protons within

1608-414: Is essential to the production of nuclear power. In the decade after the neutron was discovered by James Chadwick in 1932, neutrons were used to induce many different types of nuclear transmutations . With the discovery of nuclear fission in 1938, it was quickly realized that, if a fission event produced neutrons, each of these neutrons might cause and effect further fission events, in a cascade known as

1675-402: Is not affected by electric fields, but it is affected by magnetic fields. The value for the neutron's magnetic moment was first directly measured by Luis Alvarez and Felix Bloch at Berkeley, California , in 1940. Alvarez and Bloch determined the magnetic moment of the neutron to be μ n = −1.93(2)  μ N , where μ N is the nuclear magneton . The neutron's magnetic moment has

1742-479: Is related to nuclear magic numbers , the number of nucleons forming complete shells within the nucleus, e.g. 2, 8, 20, 28, 50, 82, and 126. No more than one observationally stable nuclide has the same odd neutron number, except for 1 ( H and He), 5 ( Be and B), 7 ( C and N), 55 ( Mo and Ru), and 107 ( Hf and Ta). In contrast, all even neutron numbers from 6 to 124, except 84 and 86, have at least two observationally stable nuclides. Neutron numbers for which there

1809-420: Is the reduced Planck constant . For many years after the discovery of the neutron, its exact spin was ambiguous. Although it was assumed to be a spin  ⁠ 1 / 2 ⁠ Dirac particle , the possibility that the neutron was a spin  ⁠ 3 / 2 ⁠ particle lingered. The interactions of the neutron's magnetic moment with an external magnetic field were exploited to finally determine

1876-681: The Chicago Pile-1 at the University of Chicago in 1942, the first self-sustaining nuclear reactor . Just three years later the Manhattan Project was able to test the first atomic bomb , the Trinity nuclear test in July 1945. The mass of a neutron cannot be directly determined by mass spectrometry since it has no electric charge. But since the masses of a proton and of a deuteron can be measured with

1943-595: The Earth's crust . An atomic nucleus is formed by a number of protons, Z (the atomic number ), and a number of neutrons, N (the neutron number ), bound together by the nuclear force . Protons and neutrons each have a mass of approximately one dalton . The atomic number determines the chemical properties of the atom, and the neutron number determines the isotope or nuclide . The terms isotope and nuclide are often used synonymously , but they refer to chemical and nuclear properties, respectively. Isotopes are nuclides with

2010-503: The strong force . Furthermore, the complex system of quarks and gluons that constitute a neutron requires a relativistic treatment. But the nucleon magnetic moment has been successfully computed numerically from first principles , including all of the effects mentioned and using more realistic values for the quark masses. The calculation gave results that were in fair agreement with measurement, but it required significant computing resources. Chemical properties A chemical property

2077-501: The 1944 Nobel Prize in Chemistry "for his discovery of the fission of heavy atomic nuclei". The discovery of nuclear fission would lead to the development of nuclear power and the atomic bomb by the end of World War II. It was quickly realized that, if a fission event produced neutrons, each of these neutrons might cause further fission events, in a cascade known as a nuclear chain reaction. These events and findings led Fermi to construct

Neutron - Misplaced Pages Continue

2144-533: The Nobel Prize in Physics "for his demonstrations of the existence of new radioactive elements produced by neutron irradiation, and for his related discovery of nuclear reactions brought about by slow neutrons". In December 1938 Otto Hahn , Lise Meitner , and Fritz Strassmann discovered nuclear fission , or the fractionation of uranium nuclei into lighter elements, induced by neutron bombardment. In 1945 Hahn received

2211-442: The Standard Model for particle physics, a neutron comprises two down quarks with charge − ⁠ 1 / 3 ⁠ e and one up quark with charge + ⁠ 2 / 3 ⁠ e . The neutron is therefore a composite particle classified as a hadron . The neutron is also classified as a baryon , because it is composed of three valence quarks . The finite size of the neutron and its magnetic moment both indicate that

2278-445: The Standard Model, in 1964 Mirza A.B. Beg, Benjamin W. Lee , and Abraham Pais calculated the ratio of proton to neutron magnetic moments to be −3/2 (or a ratio of −1.5), which agrees with the experimental value to within 3%. The measured value for this ratio is −1.459 898 05 (34) . The above treatment compares neutrons with protons, allowing the complex behavior of quarks to be subtracted out between models, and merely exploring what

2345-406: The beta decay process. The neutrons and protons in a nucleus form a quantum mechanical system according to the nuclear shell model . Protons and neutrons of a nuclide are organized into discrete hierarchical energy levels with unique quantum numbers . Nucleon decay within a nucleus can occur if allowed by basic energy conservation and quantum mechanical constraints. The decay products, that is,

2412-512: The boundary between chemistry and physics , the distinction may be a matter of researcher's perspective . Material properties , both physical and chemical, can be viewed as supervenient ; i.e., secondary to the underlying reality. Several layers of superveniency are possible. Chemical properties can be used for building chemical classifications . They can also be useful to identify an unknown substance or to separate or purify it from other substances. Materials science will normally consider

2479-465: The capture of a lepton by the nucleon. The transformation of a proton to a neutron inside of a nucleus is possible through electron capture : A rarer reaction, inverse beta decay , involves the capture of a neutrino by a nucleon. Rarer still, positron capture by neutrons can occur in the high-temperature environment of stars. Three types of beta decay in competition are illustrated by the single isotope copper-64 (29 protons, 35 neutrons), which has

2546-737: The chemical properties of a substance to guide its applications. This chemistry -related article is a stub . You can help Misplaced Pages by expanding it . Isotone In nuclear physics , isotones are nucleides of the different chemical elements . They have the same neutron number , but different nucleon number (mass number) due to different proton number (atomic number). For example, boron-12 and carbon-13 nuclei both contain 7 neutrons , and so are isotones. Similarly, S, Cl, Ar, K, and Ca nuclei are all isotones of 20 because they all contain 20 neutrons. The term derives from Greek ἴσος (isos)  'same' and τόνος (tonos)  'tension' metaphorically suggesting

2613-434: The common chemical element lead , Pb, has 82 protons and 126 neutrons, for example. The table of nuclides comprises all the known nuclides. Even though it is not a chemical element, the neutron is included in this table. Protons and neutrons behave almost identically under the influence of the nuclear force within the nucleus. They are therefore both referred to collectively as nucleons . The concept of isospin , in which

2680-417: The constituent quarks. The calculation assumes that the quarks behave like point-like Dirac particles, each having their own magnetic moment. Simplistically, the magnetic moment of the neutron can be viewed as resulting from the vector sum of the three quark magnetic moments, plus the orbital magnetic moments caused by the movement of the three charged quarks within the neutron. In one of the early successes of

2747-543: The difference in mass represents the mass equivalent to nuclear binding energy, the energy which would need to be added to take the nucleus apart. The nucleus of the most common isotope of the hydrogen atom (with the chemical symbol H) is a lone proton. The nuclei of the heavy hydrogen isotopes deuterium (D or H) and tritium (T or H) contain one proton bound to one and two neutrons, respectively. All other types of atomic nuclei are composed of two or more protons and various numbers of neutrons. The most common nuclide of

Neutron - Misplaced Pages Continue

2814-515: The effects would be of differing quark charges (or quark type). Such calculations are enough to show that the interior of neutrons is very much like that of protons, save for the difference in quark composition with a down quark in the neutron replacing an up quark in the proton. The neutron magnetic moment can be roughly computed by assuming a simple nonrelativistic , quantum mechanical wavefunction for baryons composed of three quarks. A straightforward calculation gives fairly accurate estimates for

2881-459: The electron fails to gain the 13.6  eV necessary energy to escape the proton (the ionization energy of hydrogen ), and therefore simply remains bound to it, forming a neutral hydrogen atom (one of the "two bodies"). In this type of free neutron decay, almost all of the neutron decay energy is carried off by the antineutrino (the other "body"). (The hydrogen atom recoils with a speed of only about (decay energy)/(hydrogen rest energy) times

2948-405: The emitted particles, carry away the energy excess as a nucleon falls from one quantum state to one with less energy, while the neutron (or proton) changes to a proton (or neutron). For a neutron to decay, the resulting proton requires an available state at lower energy than the initial neutron state. In stable nuclei the possible lower energy states are all filled, meaning each state is occupied by

3015-447: The extraordinary developments in atomic physics that occurred in the first half of the 20th century, leading ultimately to the atomic bomb in 1945. In the 1911 Rutherford model , the atom consisted of a small positively charged massive nucleus surrounded by a much larger cloud of negatively charged electrons. In 1920, Ernest Rutherford suggested that the nucleus consisted of positive protons and neutrally charged particles, suggested to be

3082-474: The gamma ray interpretation. Chadwick quickly performed a series of experiments that showed that the new radiation consisted of uncharged particles with about the same mass as the proton. These properties matched Rutherford's hypothesized neutron. Chadwick won the 1935 Nobel Prize in Physics for this discovery. Models for an atomic nucleus consisting of protons and neutrons were quickly developed by Werner Heisenberg and others. The proton–neutron model explained

3149-572: The isotopes of the same species were found to have either integer or fractional spin. By the hypothesis, isotopes would be composed of the same number of protons, but differing numbers of neutral bound proton+electron "particles". This physical picture was a contradiction, since there is no way to arrange the spins of an electron and a proton in a bound state to get a fractional spin. In 1931, Walther Bothe and Herbert Becker found that if alpha particle radiation from polonium fell on beryllium , boron , or lithium , an unusually penetrating radiation

3216-474: The long-range electromagnetic force , but the much stronger, but short-range, nuclear force binds the nucleons closely together. Neutrons are required for the stability of nuclei, with the exception of the single-proton hydrogen nucleus. Neutrons are produced copiously in nuclear fission and fusion . They are a primary contributor to the nucleosynthesis of chemical elements within stars through fission, fusion, and neutron capture processes. The neutron

3283-413: The magnetic moments of neutrons, protons, and other baryons. For a neutron, the result of this calculation is that the magnetic moment of the neutron is given by μ n = 4/3 μ d − 1/3 μ u , where μ d and μ u are the magnetic moments for the down and up quarks, respectively. This result combines the intrinsic magnetic moments of the quarks with their orbital magnetic moments, and assumes

3350-453: The neutron are described below in the Intrinsic properties section . Outside the nucleus, free neutrons undergo beta decay with a mean lifetime of about 14 minutes, 38 seconds, corresponding to a half-life of about 10 minutes, 11 s. The mass of the neutron is greater than that of the proton by 1.293 32   MeV/ c , hence the neutron's mass provides energy sufficient for the creation of

3417-415: The neutron is a composite , rather than elementary , particle. The quarks of the neutron are held together by the strong force , mediated by gluons . The nuclear force results from secondary effects of the more fundamental strong force . The only possible decay mode for the neutron that obeys the conservation law for the baryon number is for one of the neutron's quarks to change flavour (through

SECTION 50

#1732851412723

3484-416: The nucleus via the nuclear force , effectively moderating the repulsive forces between the protons and stabilizing the nucleus. Heavy nuclei carry a large positive charge, hence they require "extra" neutrons to be stable. While a free neutron is unstable and a free proton is stable, within nuclei neutrons are often stable and protons are sometimes unstable. When bound within a nucleus, nucleons can decay by

3551-466: The nuclide to become unstable and break into lighter nuclides and additional neutrons. The positively charged light nuclides, or "fission fragments", then repel, releasing electromagnetic potential energy . If this reaction occurs within a mass of fissile material , the additional neutrons cause additional fission events, inducing a cascade known as a nuclear chain reaction . For a given mass of fissile material, such nuclear reactions release energy that

3618-440: The original particle is not composed of the product particles; rather, the product particles are created at the instant of the reaction. "Free" neutrons or protons are nucleons that exist independently, free of any nucleus. The free neutron has a mass of 939 565 413 .3  eV/ c , or 939.565 4133   MeV/ c . This mass is equal to 1.674 927 471 × 10  kg , or 1.008 664 915 88   Da . The neutron has

3685-401: The primordial radionuclide Xe). Neutron numbers for which there are no stable isotones are 19, 21, 35, 39, 45, 61, 89, 115, 123, and 127 or more (though 21, 142, 143, 146, and perhaps 150 have primordial radionuclides). In contrast, the proton numbers for which there are no stable isotopes are 43 , 61 , and 83 or more (83, 90 , 92 , and perhaps 94 have primordial radionuclides). This

3752-463: The proton and neutron are viewed as two quantum states of the same particle, is used to model the interactions of nucleons by the nuclear or weak forces. Because of the strength of the nuclear force at short distances, the nuclear energy binding nucleons is many orders of magnitude greater than the electromagnetic energy binding electrons in atoms. In nuclear fission , the absorption of a neutron by some heavy nuclides (such as uranium-235 ) can cause

3819-405: The proton, electron and electron anti- neutrino decay products, and where n , e , and ν e denote the neutron, positron and electron neutrino decay products. The electron and positron produced in these reactions are historically known as beta particles , denoted β or β respectively, lending the name to the decay process. In these reactions,

3886-461: The proton, electron, and anti-neutrino. In the decay process, the proton, electron, and electron anti-neutrino conserve the energy, charge, and lepton number of the neutron. The electron can acquire a kinetic energy up to 0.782 ± 0.013 MeV . Still unexplained, different experimental methods for measuring the neutron's lifetime, the "bottle" and "beam" methods, produce different values for it. The "bottle" method employs "cold" neutrons trapped in

3953-516: The puzzle of nuclear spins. The origins of beta radiation were explained by Enrico Fermi in 1934 by the process of beta decay , in which the neutron decays to a proton by creating an electron and a (at the time undiscovered) neutrino. In 1935, Chadwick and his doctoral student Maurice Goldhaber reported the first accurate measurement of the mass of the neutron. By 1934, Fermi had bombarded heavier elements with neutrons to induce radioactivity in elements of high atomic number. In 1938, Fermi received

4020-427: The same atomic number, but different neutron number. Nuclides with the same neutron number, but different atomic number, are called isotones . The atomic mass number , A , is equal to the sum of atomic and neutron numbers. Nuclides with the same atomic mass number, but different atomic and neutron numbers, are called isobars . The mass of a nucleus is always slightly less than the sum of its proton and neutron masses:

4087-428: The speed of light, or 250  km/s .) Neutrons are a necessary constituent of any atomic nucleus that contains more than one proton. As a result of their positive charges, interacting protons have a mutual electromagnetic repulsion that is stronger than their attractive nuclear interaction , so proton-only nuclei are unstable (see diproton and neutron–proton ratio ). Neutrons bind with protons and one another in

SECTION 60

#1732851412723

4154-437: The spin of the neutron. In 1949, Hughes and Burgy measured neutrons reflected from a ferromagnetic mirror and found that the angular distribution of the reflections was consistent with spin  ⁠ 1 / 2 ⁠ . In 1954, Sherwood, Stephenson, and Bernstein employed neutrons in a Stern–Gerlach experiment that used a magnetic field to separate the neutron spin states. They recorded two such spin states, consistent with

4221-483: The three quarks are in a particular, dominant quantum state. The results of this calculation are encouraging, but the masses of the up or down quarks were assumed to be 1/3 the mass of a nucleon. The masses of the quarks are actually only about 1% that of a nucleon. The discrepancy stems from the complexity of the Standard Model for nucleons, where most of their mass originates in the gluon fields, virtual particles, and their associated energy that are essential aspects of

4288-451: The uniformity in one property (neutron count). It was formed by the German physicist K. Guggenheimer by changing the "p" in " isotope " from "p" for "proton" to "n" for "neutron". The largest numbers of observationally stable nuclides exist for isotones 50 (five: Kr, Sr, Y, Zr, Mo – noting also the primordial radionuclide Rb) and 82 (six: Ba, La, Ce, Pr, Nd, Sm – noting also

4355-402: The weak force. The decay of one of the proton's up quarks into a down quark can be achieved by the emission of a W boson. The proton decays into a neutron, a positron, and an electron neutrino. This reaction can only occur within an atomic nucleus which has a quantum state at lower energy available for the created neutron. The story of the discovery of the neutron and its properties is central to

4422-570: Was difficult to reconcile the proton–electron model of the nucleus with the Heisenberg uncertainty relation of quantum mechanics. The Klein paradox , discovered by Oskar Klein in 1928, presented further quantum mechanical objections to the notion of an electron confined within a nucleus. The observed properties of atoms and molecules were inconsistent with the nuclear spin expected from the proton–electron hypothesis. Protons and electrons both carry an intrinsic spin of ⁠ 1 / 2 ⁠ ħ , and

4489-606: Was produced. The radiation was not influenced by an electric field, so Bothe and Becker assumed it was gamma radiation . The following year Irène Joliot-Curie and Frédéric Joliot-Curie in Paris showed that if this "gamma" radiation fell on paraffin , or any other hydrogen -containing compound, it ejected protons of very high energy. Neither Rutherford nor James Chadwick at the Cavendish Laboratory in Cambridge were convinced by

#722277