Wolfgang Pauli
The Pauli Exclusion Principle
In physics, a quantum number is a set of integers (or half-integers) that identify the state of a physical system . Quantum numbers can be applied to atoms, nuclei, or subatomic particles (electrons, protons, etc) [1]. The Pauli Exclusion Principle deals with the quantum numbers of electrons, so before we dive into explaining the exclusion principle, lets go over the quantum numbers for electrons.
Every electron has four quantum numbers: n, l, m, and s (sometimes these are also designated n, l, ml, and ms) [2]. N is the principle quantum number, and can range from 1 to infinity. The n value corresponds to what electron shell an electron is in [3]. For example, an electron with an n of 2 would be in the 2nd electron shell.
L is the orbital angular momentum quantum number and can range from 0 to n-1. The l value signifies what type of subshell or orbital the electron is in. There are four types of subshells: s, p, d, and f. The table below explains what l values correspond to which subshells [4].
| L value |
Subshell/Orbital |
| 0 | s |
| 1 | p |
| 2 | d |
| 3 | f |
If an electron had an n value of 3 and an l value of 1 we would know that the electron occupied a p orbital in the 3rd electron shell.
M is the magnetic quantum number and can range from –l to +l. M is related to the orientation of orbitals within a subshell. So if an electron had an l value of 2, m could be -2, -1, 0, 1, or 2 [5].
S is the electron spin quantum number, and for an electron, it can be either -½ or +½ [6]. Any two electrons in the same orbital will have opposite spins [7].
Now that we understand quantum numbers of
electrons, we can dive into the Pauli exclusion principle.
The Pauli Exclusion Principle: Any
two electrons in the same atom cannot have the
same set of
quantum numbers [8].
Pauli’s exclusion
principle can apply to more than just electrons. Subatomic
particles that obey the exclusion principle are called
fermions, and include particles such as protons, neutrons,
muons, lambda particles, and more [9].
Subatomic particles that do not follow the exclusion
principle are called bosons [10].
Neutrinos
Although Pauli’s arguably
best-known contribution to physics was his discovery of
the Pauli exclusion principle, another important
achievement was his proposal of the neutrino.
Wolfgang Pauli proposed the
basic properties of electron-neutrinos in 1930 to explain
why energy appeared to be lost during radioactive beta
decay [11]. It took 20 years
before neutrinos were experimentally detected. Neutrinos
rarely interact with matter (due in part to their lack of
charge), which is part of what made them difficult to
detect experimentally [12].
Neutrinos are a type of lepton (a family of subatomic particles) with no charge, little mass, and a ½ unit of spin [13]. There are three different kinds of neutrinos: the electron-neutrino, muon-neutrino, and tau-neutrino [14].
Works Cited
[1] Quantum number. Encyclopaedia Britannica.
[2] Kotz, Treichel, Townsend. General Chemistry I.
[3] Kotz, Treichel, Townsend. General Chemistry I.
[4] Kotz, Treichel, Townsend. General Chemistry I.
[5] Kotz, Treichel, Townsend.
General Chemistry I.
[6] Kotz,
Treichel, Townsend. General Chemistry I.
[7] Kotz, Treichel, Townsend. General
Chemistry I.
[8] Wolfgang
Pauli- Facts. Nobelprize.org
[9] Pauli
Exclusion Principle. Encyclopaedia Britannica.
[10] Pauli
Exclusion Principle. Encyclopaedia Britannica.
[11] Neutrino.
Encyclopaedia Britannica.
[12] Neutrino.
Encyclopaedia Britannica.
[13] Neutrino.
Encyclopaedia Britannica.
[14] Neutrino.
Encyclopaedia Britannica.