In quantum mechanics, a fermionic atom is an atom in which the electrons are assumed to be spin-1/2 fermions. The word “fermion” comes from the Italian physicist Enrico Fermi. The term “atom” comes from the Greek ἄτομος (átomos), meaning indivisible. In contrast, bosonic atoms have integer spin and are composed of bosons.
The Pauli exclusion principle requires that no two fermions can occupy the same quantum state. This has profound consequences for the behavior of fermionic atoms. For example, it implies that those atoms cannot be Bose–Einstein condensed because there would be too many atoms in the ground state. It also explains why most atoms are monatomic: if two electrons were in the same orbital they would violate the exclusion principle.
Fermionic atoms have been studied extensively both theoretically and experimentally. They play an important role in our understanding of atomic physics and chemical bonding, and their properties are essential for applications such as semiconductor devices and superconductors.