exclusion principle
  • The rule that not more than one particle can have the same quantum conditions in the same atom. They must differ in energy level, spin or some other characteristic. Also called the Pauli Exclusion Principle after Swiss physicist Wolfgang Pauli (1900–1958) this rule is fundamental to nuclear structure and in astrophysics is vital to understanding how white dwarfs and neutron stars are formed.
  • A principle that states that no two fermions can occupy the same quantum state. In the case of electrons, for instance, this means that two electrons in the same atom can not have the same values of all quantum numbers. This leads to there only being able to be two electrons, each with opposite spin, in the same atomic orbital. Also called Pauli exclusion principle, or Pauli principle.

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