See Also: Orbital(medicine)
orbital fat-pad(medicine)
orbital rim(medicine)
orbital(dictionary)
orbital(encyclopedia)
zygomatico-orbital(medicine)
orbital process(medicine)
orbital 1, adjective(dictionary)
orbital plane(medicine)
orbital ophthalmoplegia(medicine)

orbital (sh)




Mathematical expression, called a wave function, that describes properties characteristic of no more than two electrons near an atomic nucleus or molecule.

An orbital can be considered a three-dimensional region in which there is a 95% probability of finding an electron. Atomic orbitals are designated by a combination of numerals and letters (e.g., 1s, 2p, 3d, 4f). The numerals are the principal quantum number and are related to the atomic energy level and distance from the nucleus; the letters indicate the orbital's angular momentum and hence its shape. An s orbital with zero net orbital angular momentum is spherical. A p orbital with one fundamental unit of angular momentum, ?, is shaped somewhat like a dumbbell (? is Planck's constant, h, divided by 2¦Ð). The shapes of the other orbitals are more complicated. Molecular orbitals have geometries determined by the overlap of two or more atomic orbitals and are designated by Greek symbols, e.g., ¦Ò and ¦Ð.