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Four quantum numbers can describe an electron energy level in a hydrogen-like atom completely: Principal quantum number (n) Azimuthal quantum number (ℓ) Magnetic quantum number (m ℓ) Spin quantum number (m s) These quantum numbers are also used in the classical description of nuclear particle states (e.g. protons and neutrons).
A common example of quantum numbers is the possible state of an electron in a central potential: (,,,), which corresponds to the eigenstate of observables (in terms of ), (magnitude of angular momentum), (angular momentum in -direction), and .
Each distinct n, ℓ, m ℓ orbital can be occupied by two electrons with opposing spins (given by the quantum number m s = ± 1 ⁄ 2), giving 2(2ℓ + 1) electrons overall. Orbitals with higher ℓ than given in the table are perfectly permissible, but these values cover all atoms so far discovered.
In the terminology of atomic spectroscopy, L and S together specify a term; L, S, and J specify a level; and L, S, J and the magnetic quantum number M J specify a state. The conventional term symbol has the form 2S+1 L J, where J is written optionally in order to specify a level.
Once good quantum numbers have been found for a given atomic transition, the selection rules determine what changes in quantum numbers are allowed. The electric dipole (E1) transition of a hydrogen atom can be described with the quantum numbers l (orbital angular momentum quantum number), m l (magnetic quantum number), m s (electron spin ...
Other magnetic quantum numbers are similarly defined, such as m j for the z-axis component the total electronic angular momentum j, [1] and m I for the nuclear spin I. [2] Magnetic quantum numbers are capitalized to indicate totals for a system of particles, such as M L or m L for the total z-axis orbital angular momentum of all the electrons ...
Some introductory chemistry textbooks describe m s as the spin quantum number, [6] [7] and s is not mentioned since its value 1 / 2 is a fixed property of the electron; some even use the variable s in place of m s. [5] The two spin quantum numbers and are the spin angular momentum analogs of the two orbital angular momentum quantum ...
The four quantum numbers n, ℓ, m, and s specify the complete and unique quantum state of a single electron in an atom, called its wave function or orbital. Two electrons belonging to the same atom cannot have the same values for all four quantum numbers, due to the Pauli exclusion principle.