what is orbital

In atomic theory and quantum mechanics, an orbital is a mathematical expression, called a wave function, that describes properties characteristic of no more than two electrons in the vicinity of an atomic nucleus. It is a three-dimensional description of the most likely location of an electron around an atom. Orbitals are combined when bonds form between atoms in a molecule. There are four types of orbitals: s, p, d, and f. Within each shell of an atom, there are some combinations of orbitals. The shape and size of an orbital can be determined from the square of the wave function Ψ2. Atomic orbitals have distinctive shapes; all are centered on the atomic nucleus. The most commonly encountered orbitals in elementary quantum chemistry are the orbitals s, p, and d subshells: these orbitals are named the s, p, and d orbitals.