What is Nucleons: Definition and 46 Discussions

In chemistry and physics, a nucleon is either a proton or a neutron, considered in its role as a component of an atomic nucleus. The number of nucleons in a nucleus defines an isotope's mass number (nucleon number).
Until the 1960s, nucleons were thought to be elementary particles, not made up of smaller parts. Now they are known to be composite particles, made of three quarks bound together by the strong interaction. The interaction between two or more nucleons is called internucleon interaction or nuclear force, which is also ultimately caused by the strong interaction. (Before the discovery of quarks, the term "strong interaction" referred to just internucleon interactions.)
Nucleons sit at the boundary where particle physics and nuclear physics overlap. Particle physics, particularly quantum chromodynamics, provides the fundamental equations that describe the properties of quarks and of the strong interaction. These equations describe quantitatively how quarks can bind together into protons and neutrons (and all the other hadrons). However, when multiple nucleons are assembled into an atomic nucleus (nuclide), these fundamental equations become too difficult to solve directly (see lattice QCD). Instead, nuclides are studied within nuclear physics, which studies nucleons and their interactions by approximations and models, such as the nuclear shell model. These models can successfully describe nuclide properties, as for example, whether or not a particular nuclide undergoes radioactive decay.
The proton and neutron are in a scheme of categories being at once fermions, hadrons and baryons. The proton carries a positive net charge, and the neutron carries a zero net charge; the proton's mass is only about 0.13% less than the neutron's. Thus, they can be viewed as two states of the same nucleon, and together form an isospin doublet (I = 1/2). In isospin space, neutrons can be transformed into protons and conversely by SU(2) symmetries. These nucleons are acted upon equally by the strong interaction, which is invariant under rotation in isospin space. According to the Noether theorem, isospin is conserved with respect to the strong interaction.

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  1. P

    I Do nucleons have a lower energy state when bound in a nucleus?

    But when I look at the definition of binding energy that doesn't make seem to make sense. It looks as though they had more energy when they were together and when they were separated that energy turned to mass (the mass defect)? Am I looking at this right? I also don't understand this...
  2. vintagelover007

    Fermi Motion of Nucleons due to a Beam of Neutrinos

    Stable nuclei have radii that are approximately given by the formula: R = r0_A^1/3 Where r0 = 1.25 × 10−15m and A is the atomic mass number. In many experiments of interest to modern particle physics, beams of neutrinos scatter from nucleons within the nucleus. Even though the nucleus is at...
  3. PainterGuy

    B Why does the nucleus become unstable as the number of nucleons increases?

    Hi, I'd appreciate it if you could help me with the queries below. Please try to keep it as simple as possible because I have only basic understanding. Source: https://www.nde-ed.org/EducationResources/HighSchool/Radiography/radioactivity.htm Source...
  4. E

    B Rest energies of individual nucleons considered in isolation

    I'm conscious I posted a question about a similar topic recently, however I can't seem to resolve an apparent contradiction. As an example, consider a deuterium atom with 1 proton and 1 neutron. When separated at infinity, each has a certain mass and a certain rest energy differing only by a...
  5. Javier Lopez

    I What are the magnetic states of nucleons?

    Could I have hundred times the ground state or there is a limit? Is there a limit for excited magnetic momentum that if reached the nucleous explode or generate gammas? I suppose If I excite it it would spin faster but proportional to quantum values. Note: there is a "theory" to avoid electron...
  6. Krushnaraj Pandya

    B Is the Force Between Two Protons Weaker Than Between Two Neutrons in Nucleons?

    My question is whether the force between two protons is slightly less than the force between two neutrons as you'd expect from the electrostatic repulsion or does the strong nuclear force somehow treat all nucleons such that they have the same force acting between them? I'd really appreciate...
  7. S

    I Distribution of nucleons in the nuclei

    What does this diagram tell us about the distribution of nucleons in the nuclei? - The diagram is from Krane Introductory Nuclear Physics I know that nucleons don't congregate around a central part of a nucleus, but instead have a constant distribution throughout. i.e. The number of nucleons...
  8. C

    I Distance between two nucleons

    The potential energy associated to the interaction between nucleons has its minimum (point of equilibrium) at ##r\sim 0.7 fm##, as showed in the following graph: Nevertheless, there are two facts that are, apparently, in contrast with this: - The average distance between nucleons is...
  9. H

    I Are new nucleons formed in heavy-ion collisions?

    The subject heading says it all. In heavy-ion high energy collisions that form a quark gluon plasma (QGP), is it known whether new nucleons are formed from the added energy, or are all of the QGP's quarks ones that existed previously in the colliding heavy ion nuclei? More specifically, are...
  10. J

    I How to derive number of nucleons in Universe?

    I understand that there are roughly ##N=10^{79}## nucleons in the visible Universe. This number comes from adding up the nucleons of ##100## billion stars in ##100## billion galaxies in the visible Universe i.e. $$N=\frac{10^{30}}{10^{-27}}. 10^{11}.10^{11}=10^{79}$$ where mass of sun is...
  11. K

    B What causes mass defect in the nucleus?

    Hi. I read that the mass of nucleons in nucleus of Oxygen-16 (or nucleus of another atom) is less than the sum of its nucleons if they were separated (also the mass of 8 protons and 8 neutrons). But why does nucleons have less energy in nucleus of atoms than if they were separated? What causes...
  12. A

    I The strong interaction outside nucleons - what mediates it?

    The strong interaction outside nucleons - what mediates it? Is it gluons? Is it mesons? Is it gluons within mesons? Thank you.
  13. moenste

    KE of alpha particle using integer values of nuclear masses

    Homework Statement (a) Cobalt has only one stable isotope, 59Co. What form of radioactive decay would you expect the isotope 60Co to undergo? Give a reason for your answer. (b) The radioactive nuclei 21084Po emit alpha particles of a single energy, the product nuclei being 20682Pb. (b) (i)...
  14. Davephaelon

    I Is Unruh Radiation from Quarks in Nucleons a Violation of Energy Conservation?

    Back in 2005 Shahar Hod submitted a paper (http://arxiv.org/abs/hep-th/0510089) proposing that Unruh radiation from quarks inside nucleons is of a magnitude comparable to the mass of a quark. This concept has been discussed in previous threads...
  15. Anonymous Vegetable

    What is the reason for mass defect in a nuclide?

    I may be misguided here but to my understanding, separate nucleons have a higher mass altogether than the combined nucleus as the potential energy gained from being separated (in the field of the strong force) is being manifested in more mass. If this is true, and if it's not I'd like to know...
  16. D

    Are quarks shared between nucleons?

    Homework Statement This is not a homework question, I'm asking it here to avoid being shot down elsewhere. Are quarks tightly bound to each nucleon? Is the nucleus just a bunch of anonymous quarks held together by the strong nuclear force, or is each proton and neutron separate? When...
  17. N

    Neutrinos incident on target - interaction with nucleons or nuclei?

    I came across a worked example question in a particle physics book this morning that had a beam of neutrinos of energy 2.3MeV incident on a lead target. The point of the question was calculating the thickness of lead needed to reduce the beam intensity by a certain fraction - and the solution...
  18. D

    Pauli exclusion regarding nucleons

    I think this is more or less a quick question. So deuteron (pn) is an isosinglet in the state |00> =\frac{1}{\sqrt{2}}(pn-np) since it cannot be part of the isotriplet that includes pp and nn, since these violate pauli exclusion. That's fine. So how is it that we can have atoms like...
  19. Superposed_Cat

    Difference between delta baryons and nucleons

    Hello, I have had this question for awhile now. What is the difference a delta baryon and a nucleon? they seem to have the same quark composition? Thanks in advance.
  20. C

    High temperatures, nucleons, early universe

    Homework Statement At very high temperatures (as in the very early universe), the proton ad neutron can be thought of as two different states of the same particle, called the "nucleon". (The reactions that convert a proton to a neutron or vice versa require the absorption of an electron or a...
  21. J

    Nucleons, mass defect, and mass

    in high school we are learning about mass defect in nuclear fission and fusion and I know the math: ΔE=Δmc^2 however often the mass changed into energy is much less then the mass of a single nucleon(proton or neutron) and there are no fewer nucleons. for this to happen I would think that you...
  22. S

    Mass Defect & the Strong Force in Nucleons

    I was wondering how mesons or the strong force is accounted for in mass defect. Nucleons individually have more mass then when they are bound together in a nucleus of an atom. I saw a teacher/professor speak on youtube. He said the binding energy (strong force) was calculated as part of the...
  23. jaketodd

    Discover the Velocities of Nucleons | Proton, Neutron and More

    Thanks everyone for your help over the years... Much appreciated if someone will tell me: A) The velocities of the proton and neutron in Deuterium/Hydrogen2 B) How to calculate the velocities of nucleons for arbitrary atoms
  24. J

    How do you calculate the strong isospin of nucleons?

    First post, so hi everyone. I have been banging my head against this question for a little while now. I've found two methods that appear to give the same result, but am not quite happy with what I've done: Homework Statement Calculate the strong isospin components of both tritium (3H)...
  25. W

    Odd vs. Even number of Nucleons.

    Yeah I'm taking this introductory nuclear science class, we're reading Rhodes's Making of the Atomic Bomb. Apparently, U235 with a neutron added now has an even number of nucleons while U238 obviously has an odd number with the single neutron bombarment. And this affects fission likelihood. So...
  26. D

    Exploring the Effects of Energy Loss on Nucleons

    Hi there... My question is that when nucleon's loses energy (such as in fusion),does that affect their size as well? do they also shrink or grow by losing or gaining energy?
  27. T

    Estimating Nucleons in a 85 kg person.

    Homework Statement Estimate the number of nucleons found in the body of a 85 kg person. Homework Equations The Attempt at a Solution This all of the information they give for this problem so I am not sure what equations or what other numbers to use.
  28. R

    Classical radius of nucleons and quarks

    hi, how do you calculate the classical radius of nucleons or quarks? do you include only the electrostatic potential energy or also some nuclear potential energy?. i have read many times that the classical radius of nucleons is lower than the classical radius of the electron, is it right...
  29. J

    Stable nucleons other than Neutrons and Protons?

    Can there be any particle other than a proton or a neutron that can remain stably in the nucleus of an atom at ordinary temperatures and pressures? I'm aware of hypernuclei (nuclei containing hyperons) but none of those are stable. I understand that they all decay weakly. Is there any...
  30. D

    Nucleus Ratio of nucleons between surface and core

    Homework Statement We suppose the nucleon density of a spherical nucleus where r<R1 is constant, and where R1<r<R2 the density linearly decreases to 0 at R2. We call the surface nucleons (Number Ns) the number of nucleons contained in the volume R1<r<R2 and core nucleons (Nc) the number...
  31. R

    Could Halo Nucleons Affect Electron Capture in Nuclear Decay?

    Hypothetically, could the process of electron capture in any way be affected by the presence of halo nucleons? There is probably little relation if any, I don't even think that any nuclear of the known halo isotopes can undergo decay under k-capture.
  32. JK423

    Can positive energy nucleons be bound together in nuclear forces?

    Say we have a proton and a neutron. How can we get them bound to form a deuteron? If the neutron is still in the lab's framework, we bombard it with protons with such a kinetic energy that they can form a deuteron with the neutrons. But if we look at the potential of the nuclear force between...
  33. D

    Quark spatial change in nucleons & nuclear stability

    I am curious to know if there have been any experiments to measure change in nuclear disintegration rates/ gamma emissions with change of distance between quarks in nucleons? Thank you. Douglas
  34. M

    Total Angular Momentum of Two Nucleons: Possible Values?

    Homework Statement The spin of each of the two nucleons is 3/2 with Sz=0 . The orbital angular momentum b/w the two nucleons is zero . What values can the total angular momentum have ? Homework Equations The Attempt at a Solution This was a question in my exam and i got stuck , so...
  35. C

    Parity of nucleons and fission

    Can anyone explain this to me? It piqued my interest, especially since I nominally work with radioactive materials (though admittedly, not fissile material) and didn't know where this came from. "It is not a coincidence, for example, that the three nuclei which are fissionable with slow...
  36. R

    Infinite Square Well and nucleons

    Homework Statement Twelve nucleons are in a one dimensional infinite square well of length L = 3 fm. Using a mass of 1 u. What is the ground state energy of the system of 12 nucleons in the well if all the nucleons are neutrons so that there can only be 2 in each state. Homework...
  37. A

    Nuclear physics - number of nucleons on surface?

    Homework Statement For a nucleus of A=220, estimate very roughly how many nucleaons would be at the surface. Homework Equations R0=1.5 x 10-15 r=A1/3 x R0 The Attempt at a Solution Using the formulas, I calculated R to be 7.2441729 x 10-15 The book says that the number of...
  38. E

    What are the shape of nucleons and quarks?

    When one of the quarks was discovered, I was in high school, and I said quarks are not spherical balls of mass. How could nucleons also be spheres if 3 quarks make up a nucleon?! I said atomic and subatomic particles have a poorly defined shape and something of a lack of material substance...
  39. C

    Is it possible that gravitons also orbit nucleons like electrons do?

    Is it possible that gravitons also orbit nucleons like electrons do? I know this is speculative grounds, but are there any scientific principles that come to mind that could fallsify this question?
  40. K

    Quark composition of nucleons : dimensionality ?

    As a layperson, I read that nuclei components nucleons(n,p) are normally built up of three quarks. But does that number of particle not define only a plane (outside the radii of quarks themselves)...Are nucleon having only a surface (or a volume wiht 1 negligeable length) and not a volume ...
  41. marcus

    Unruh-ly radiation inside nucleons

    in case anyone is interested Unruh radiation is somewhat like Hawking radiation, a quantum gravity thing----so I will post it here http://www.arxiv.org/abs/hep-th/0510089 Unruh Radiation in Atomic and Nuclear Systems Shahar Hod 2 pages "We analyze the Unruh radiation effect experienced by...
  42. E

    Why don't ups and downs annihilate in nucleons?

    Answer me that! Because they should, shouldn't they? Strong attractive forces, attractive EM forces... you'd think nothing would separate them.
  43. A

    Binding energy between nucleons vs BE inside nucleons

    humm, I've been wondering: the mass of a nucleus is less than the sum of the masses of the constituent nucleons because of the binding energy. This is how we can get energy out of fusion and fission events. on the other hand, the mass of a proton or a neutron is MORE than the sum of the...
  44. quasar987

    Exploring Mass-Energy Equivalence and Nucleons

    I was thinking just a moment ago and fragments of random knowledge and ideas gathered to make this question... If I remember my college physics class correctly, an evidence of the mass-energy equivalence is that in an atom, the sum of the rest masses of the nucleons is greater than the rest...
  45. humanino

    Proving Spin 1/2 of Nucleons: Theory & Experiment

    How well are we certain that nucleon have spin one half ? I see several experimental answers. I would like to have theoretical arguments, considering the fact that nucleons are not fundamental particles. How well can one apply lorentz symmetry to the free neutron which is not stable ? :confused: