<Li> The Slater - type orbital (STO) is a form without radial nodes but decays from the nucleus as does the hydrogen - like orbital . </Li> <Li> The form of the Gaussian type orbital (Gaussians) has no radial nodes and decays as e − α r 2 (\ displaystyle e ^ (- \ alpha r ^ (2))). </Li> <P> Although hydrogen - like orbitals are still used as pedagogical tools, the advent of computers has made STOs preferable for atoms and diatomic molecules since combinations of STOs can replace the nodes in hydrogen - like atomic orbital . Gaussians are typically used in molecules with three or more atoms . Although not as accurate by themselves as STOs, combinations of many Gaussians can attain the accuracy of hydrogen - like orbitals . </P> <P> The term "orbital" was coined by Robert Mulliken in 1932 as an abbreviation for one - electron orbital wave function . However, the idea that electrons might revolve around a compact nucleus with definite angular momentum was convincingly argued at least 19 years earlier by Niels Bohr, and the Japanese physicist Hantaro Nagaoka published an orbit - based hypothesis for electronic behavior as early as 1904 . Explaining the behavior of these electron "orbits" was one of the driving forces behind the development of quantum mechanics . </P>

Who based his model on the probability of finding an electron