Friedrich Hund

Friedrich Hund (February 4, 1896 – March 31, 1997) was a physicist known for his work on the structure of atoms and molecules.

He studied mathematics, physics, and geography in Marburg and Göttingen (Göttingen). He researched and taught (theoretical physics) at the universities of:

• Gotinga (1925)
• Harvard (1926)
• Rostock (1927)
• Copenhagen (1928)
• Leipzig (1929)
• Jena (1946)
• Frankfurt am Main (1951)
• Gotinga again (1957)

Robert Mulliken and Friedrich Hund
Chicago 1929

He has published more than 250 scientific articles and books, including "Grundbegriffe der Physik" (Fundamentals of Physics) (1969), "Geschichte der Quantentheorie" (History of Quantum Theory) (2. Ed., 1975), and "Geschichte der physikalischen Begriffe" (History of physical concepts) (2 Vol., 2. Ed., 1978).

In quantum chemistry, Hund's rule is known, which stipulates that, when at the highest level there are several orbitals with the same energy (degenerate), the spin alignment of the unpaired electrons is ferromagnetic. This explains the paramagnetism of dioxygen, and of the cations of many transition metals.

Hund's principle of maximum multiplicity: In orbitals of the same energy, electrons enter one at a time in each orbital with the same spin. When half-filling is reached, pairing with opposite spins has just begun.