exclusion principle


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exclusion principle,

physical principle enunciated by Wolfgang Pauli in 1925 stating that no two electrons in an atomatom
[Gr.,=uncuttable (indivisible)], basic unit of matter; more properly, the smallest unit of a chemical element having the properties of that element. Structure of the Atom
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 can occupy the same energy state simultaneously. The energy states, or levels, in an atom are described in the quantum theoryquantum theory,
modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity together form the theoretical basis of modern physics.
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 by various values of four different quantum numbers; the exclusion principle holds that no two electrons can have the same four quantum numbers in an atom. One of these quantum numbers describes one of the two possible directions for the electron's intrinsic spin. As a result of the exclusion principle, two electrons that are in the same energy level as described by the other three quantum numbers are differentiated from each other because they have opposite spins. This principle applies not only to atoms but to other systems containing particles as well, and it applies not only to electrons but also to a large class of particles collectively known as fermions (see elementary particleselementary particles,
the most basic physical constituents of the universe. Basic Constituents of Matter

Molecules are built up from the atom, which is the basic unit of any chemical element. The atom in turn is made from the proton, neutron, and electron.
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).

Exclusion principle

No two electrons may simultaneously occupy the same quantum state. This principle, often called the Pauli principle, was first formulated by Wolfgang Pauli in 1925 and, for time-independent quantum states, it means that no two electrons may be described by state functions which are characterized by exactly the same quantum numbers. In addition to electrons, all known particles having half-integer intrinsic angular momentum, or spin, obey the exclusion principle. It plays a central role in the understanding of many diverse phenomena, including the periodic table of the elements and their chemical activities, the electron contribution to the specific heat of metals, the shell structure in the atomic nucleus analogous to that of electrons in atoms, and certain symmetries in the scattering of identical particles. See Angular momentum, Quantum numbers, Spin (quantum mechanics)

Using the fact that a system will try to occupy the state of lowest possible energy, the electron configuration of atoms may be understood by simply filling the single-particle energy levels according to the Pauli principle. This is the basis of Niels Bohr's explanation of the periodic table. See Atomic structure and spectra, Electron configuration

exclusion principle

See Pauli exclusion principle.

exclusion principle

[ik′sklü·zhən ‚prin·sə·pəl]
(ecology)
The principle according to which two species cannot coexist in the same locality if they have identical ecological requirements.
(quantum mechanics)
The principle that no two fermions of the same kind may simultaneously occupy the same quantum state. Also known as Pauli exclusion principle.
References in periodicals archive ?
4 The broken exclusion principle and the manmade (instantaneous) magnetic monopole can be artificially created
Due to the existence of man-made laws, especially the "man-made (instantaneous) magnetic monopole" can be created as above mentioned, we can say that the broken exclusion principle can be artificially created for fermions.
5 The exclusion principle is not compatible with law of conservation of energy, and in physics the principles that are not compatible with law of conservation of energy will be invalid in some cases
Firstly the exclusion principle can be written as a symmetry form.
In order to connect the exclusion principle with a conserved quantity, supposing "1" (or any other constant) denote "valid", and "does not equal 1" denote "invalid", in this way the exclusion principle (denoted as P) can be written as the following form of conserved quantity P=1
The Pauli Exclusion Principle is an extremely important principle in science [10].
The repulsive core is attributed to the Pauli Exclusion Principle and Gillespie explains this as follows [12, see p.
QMD provides plausible explanations for various hitherto unexplained phenomena including the Pauli exclusion principle, chemical reactivity and chemical bonds.
When they found it, they discovered that it permits the existence of particles they call "parafermions" or "parons," which can violate the exclusion principle.
Helium has two electrons, and according to the exclusion principle the spins of these two electrons must always be in opposite directions.
In addition to producing unusual atomic states, the proposed violation of the exclusion principle relates to two important questions in modern particle physics, the many-dimensioned or Kaluza-Klein theories and the CPT theorem.
Greenberg doesn't know what the ultimate effects of a violation of the exclusion principle might be, but as he said at NBS, "Small-scale phenomena can have large-scale effects.