Formulated the Pauli Exclusion Principle, Fundamental to Quantum Mechanics.
Introduction
Wolfgang Ernst Pauli (circa 1900 – 1958) was an Austrian-born Swiss theoretical physicist and one of the pioneers of quantum physics.
Early Life and Education
Pauli was born in Vienna on April 25, 1900. He studied under Arnold Sommerfeld at the University of Munich and earned his Ph.D. in 1921.
Contributions
He discovered the exclusion principle or Pauli principle. The discovery involved spin theory, which is the basis of a theory of the structure of matter.
Pauli Exclusion Principle
Formulated in 1925, The quantum mechanical principle states that two identical fermions (particles with half-integer spin) cannot occupy the same quantum state simultaneously. It is impossible for two electrons of a poly-electron atom to have the same values of the four quantum numbers (n, ℓ, mℓ and ms).
For two electrons residing in the same orbital, n, ℓ, and mℓ are the same, so ms must be different, and the electrons have opposite spins.
Therefore, under certain conditions, when the orbitals of the unpaired outer valence electrons from adjacent atoms overlap, the distributions of their electric charge in space are farther apart when the electrons have parallel spins than when they have opposite spins.
This reduces the electrostatic energy of the electrons when their spins are parallel compared to their energy when the spins are anti-parallel, so the parallel-spin state is more stable. In simple terms, the electrons, which repel one another, can move “further apart” by aligning their spins, so the spins of these electrons tend to line up. This difference in energy is called the exchange energy.
The materials in which the exchange interaction is much stronger than the competing dipole-dipole interaction are frequently called magnetic materials.
For instance, in iron (Fe), the exchange force is about 1000 times stronger than the dipole interaction.
Four quantum numbers.
The four quantum numbers are the principal quantum number (n), the azimuthal or orbital quantum number (l), the magnetic quantum number (ml), He also worked on the theory of relativity, the energy spectrum of the hydrogen atom, and spin theory.and the spin quantum number (ms). These numbers describe the energy, shape, orientation, and spin of an electron in an atom.
He also worked on the theory of relativity, the energy spectrum of the hydrogen atom, and spin theory.
Quote
“For mathematical equations there are only two possibilities: either they are correct or wrong. For models there is a third one, namely correct but irrelevant.”
Legacy
- Lorentz Medal (1931)
- Nobel Prize in Physics (1945)
- Franklin Medal (1952)
- ForMemRS (1953)
- Matteucci Medal (1956)
- Max Planck Medal (1958)