Aka Friedrich Hermann Hund was a German chemist and physicist born on February 4, 1896, in Karlsruhe, Germany. It was he who developed the rule that bears his name, the Hund Rule.

He has done important work related to atomic structure and molecules, such as molecular orbitals. He also discovered the Quantum tunneling Principle (barrier in quantum penetration mechanics in spectrography).

He worked with Robert Mulliken at Gottingen University from 1927 until 1929. With Mulliken, he developed the theory of molecular orbitals.

He also worked with other leading scientists of the time such as Heisenberg and Schorodinger. He was assistant to Niels Bohr. He wrote several articles, about 250. He was a professor of physics at some universities such as Harvard, Gottingen, Rostok, Jena and Frankfurt.

In 1925 Hund empirically drafted a rule for atomic spectra, the so-called Hund Rule. It is also called the Maximum Multiplicity Principle. This rule says that the energy of an incomplete orbital is lower when there is the largest number of parallel spins electrons.

The electrons are distributed separately and with the same spin. The electrons are paired with opposite spins, that is, when filling the orbitals of the same energy level, one electron must be placed first, all with the same spin, before proceeding to full stocking of these. orbitals. The next electrons to be placed should have antiparallel spins in relation to those already present.

Hund died in Germany on March 31, 1997.