What is Quantum numbers: Definition and 122 Discussions

In chemistry and quantum physics, quantum numbers describe values of conserved quantities in the dynamics of a quantum system. Quantum numbers correspond to eigenvalues of operators that commute with the Hamiltonian—quantities that can be known with precision at the same time as the system's energy—and their corresponding eigenspaces. Together, a specification of all of the quantum numbers of a quantum system fully characterize a basis state of the system, and can in principle be measured together.
An important aspect of quantum mechanics is the quantization of many observable quantities of interest. In particular, this leads to quantum numbers that take values in discrete sets of integers or half-integers; although they could approach infinity in some cases. This distinguishes quantum mechanics from classical mechanics where the values that characterize the system such as mass, charge, or momentum, all range continuously. Quantum numbers often describe specifically the energy levels of electrons in atoms, but other possibilities include angular momentum, spin, etc. An important family is flavour quantum numbers – internal quantum numbers which determine the type of a particle and its interactions with other particles through the fundamental forces. Any quantum system can have one or more quantum numbers; it is thus difficult to list all possible quantum numbers.

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  1. K

    NEED HELP:Number of electrons with a set of quantum numbers?

    NEED URGENT HELP:Number of electrons with a set of quantum numbers? :bugeye:In one atom, what is the maximum number of electrons that can have the set of quantum numbers (n=3, l=2, ml=0, ms=+1/2)?
  2. M

    Neutron quantum numbers (NEED HELP)

    hi there, friends of physics, could anybody help me? All we know that electrons have 4 quantum numbers that describe them and -as the Pauli exclusion principle said- it can´t exist two electrons with the same quantum numbers. But I have a question, does protons and neutrons have quantum numbers...
  3. V

    Are the Quantum Numbers real ?

    I've been wondering about reality of the quantum numbers: n, l, ml and ms. We know that they are variables discovered by Balmer, Bohr, Stoner and Pauli respectively and if you plug them in the certain formula the results will match with the atomic spectrum. Well, the spectrum is certainly is the...
  4. A

    Unravelling the Mystery of J & l Quantum Numbers

    [SOLVED] Quantum Numbers What is the difference between using J and l for quantum numbers? I have some lecture notes that aren't fully explained. It was talking about rotational transitions for diatomic molecules, and said the energy of a photon going from level J to level J-1 is...
  5. L

    Confirming the Correlation of Quantum States and Lowest Quantum Numbers

    Is it generally true that the ground state of a given quantum system corresponds to the lowest quantum numbers? If so, how do we know this?
  6. U

    Electron configuration quantum numbers

    I need help with this problem :) Problem: Give the quantum numbers (n, l, ml, ms) for each electron in one neutral carbonatom in ground state. My solution: I look at a table to get the electron configuration and for a carbonatom i get 1S^2 2s^2 2p^2 For s n=1, l=0, ml=0, ms=+-1/2...
  7. G

    What Quantum Numbers Change When a Hydrogen Atom Transitions from 5d to 4f?

    A hydrogen atom is initially in the 5d state. It makes a single transition to the 4f state. List all the possible transitions that have occurred in terms of the four quantum numbers. List all
  8. B

    Angular momentum quantum numbers

    For angular momentum quantum numbers j, l, and s must it be true that m_s, m_l < m_j ? It would seem that it is true because I assume that m_s +m_l = m_j , but I have not actually seen that written down anywhere and am curious. Thanks.
  9. cepheid

    Exploring Quantum Numbers & Wavefunctions in Fermi Gas

    Hi, I have a question about the discussion of the free-electron (Fermi) gas in my solid-state physics notes. In the free electron model, you basically have particles in a box, and the state of any particle is described by four quantum numbers, nx, ny, nz, and ms, the spin magnetic quantum...
  10. L

    Quantum Numbers. Help really needed

    Homework Statement a)write a ground state electron configuration of for the arsenic atom b)give a possible set of quantum numbers for each of the three outermost electrons of the arsenic atom i know how to get the ground state, but i have no idea how to get the quantum number for each...
  11. B

    Energy levels and quantum numbers

    Hey guys, this isn't really homework but will help me on the exam and the homework too. We are working in the book, where you just get to electron structure, orbitals, configurations, etc. The part that I need help with is Quantum Numbers. My book has: n(principal energy levels)...
  12. K

    How Does n^2 Equal the Max Number of Electron Orbitals in Quantum Mechanics?

    Does anyone know how to prove, mathmatically, that the principle quantum number squared equals the maximum number of electon orbitals?any help would be appricated! n^2=max # electron orbitals
  13. G

    Finding Quantum Numbers and Eigenvectors from Matrices A & B

    Hey, I have two matrices A and B which commute. For A I have 1,-1,-1 and for B I have 1,2,2. I am asked to find the quamtum number for the three states. How to find the quantum states from the eigenvalues. It is further said that it is possible to find the eigenvectors from the quantum...
  14. P

    Understanding Quantum Numbers and Orbital Values

    The question isn't exactly like this but this is the jist of it: Give the values of the quantum numbers associated witht he following orbitals: 2p, 3s, and 5d. I ,frankly, do not understand what they are asking for. So can anyone explain this for me. Thanks.
  15. K

    Creating periodic table w/ quantum numbers

    Hello all. I have a quantum number question that is completely stumping me. "In another universe, the quantum number ml = 0, 1, 2, ... + 1. That is, the values of ml are positive integers, to a maximum value of +l. All other allowed values are unchanged, so the set of allowed values is: n...
  16. M

    Quantum Numbers for a couple of electrons Help needed

    Good evening scholars! i just had a couple of questions about QNs. ok so the problem says: Give the sets of {n, l, m, s} for the electrons in: a) 4p^2 b) 6s^2 i just want to see if I'm on the right track. here's what i put for the first one (a): n= 4 l= 1 m= -1, 0 s= +/- 1/2...
  17. S

    Quantum Numbers & Electron Energy

    Hi i was wondering what quantum numbers can change the energy of a electron within a atom. I thought it would be n and l since its the energy and sub energy numbers, but i was wrong. Can someone explain it in some more deatail please?
  18. M

    How to create good quantum states from good quantum numbers?

    how to create "good" quantum states from "good" quantum numbers? I think I am finally understanding what the "good" quantum numbers are in degenerate perturbation theroy. Basically, given a perturbation H', if [H', L^2] = [H', S^2] = [H', J^2] = [H', Jz] = 0, then l, s, j, and mj are the...
  19. R

    Quantum Numbers: Meaning & Significance

    What is the physical significance of the various quantum numbers like (l,m,s,j, etc)that are used to describe any system.
  20. V

    How Are Quantum Numbers Assigned to the Last Electron in an Aluminum Atom?

    Hi, What are the 4 quantum numbers for the last electron in the Al atom? I know how to get the primary quantum number and the spin quantum nmber, but I do not now how to get the secondary/azmuthal quantum number, and the magnetic quantum number. The book gives the secondary/azmuthal...
  21. M

    Quantum numbers of fundamental particles?

    Which are (basic?) quantum nubers of fundamental particles? I am having problems becouse a lot of expresions are used on sites on the web: el. charge, color charge, mass, taste, spin, barion & lepton number... to many :eek: :confused:
  22. benzun_1999

    Exploring Quantum Numbers: A Beginner's Guide

    hi all, What is quantum number? I know a bit about quantum number but i am not clear about it so can anyone please help me?. -Benzun, All for God.
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