The diagram to the left shows the orbitals in order of increasing energy. To the right are examples of orbital shapes.
Atomic orbitals are the places surrounding the nucleus of an atom where the electrons are most likely to be at any given time. It is a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom.
The word 'orbital' is used because it was thought that electrons behaved similarly to the solar system, where the nucleus is like the sun and the electrons orbit like the planets.
The number of atomic orbitals in an element is defined by the period the element is in. Electrons move between orbitals depending on how fast they are moving and how many other electrons there are.
In atomic theory and quantum mechanics, an atomic orbital is a quantum number. Each such orbital can be occupied by one or two electrons. The way orbitals are arranged is related to the electron configurations of atoms. They were derived from descriptions provided by early spectroscopists of certain alkali metal spectroscopic lines as being sharp, principal, diffuse, and fundamental.
Images for kids
The shapes of the first five atomic orbitals are: 1s, 2s, 2px, 2py, and 2pz. The two colors show the phase or sign of the wave function in each region. Each picture is domain coloring of a ψ(x, y, z) function which depend on the coordinates of one electron. To see the elongated shape of ψ(x, y, z)2 functions that show probability density more directly, see pictures of d-orbitals below.
Atomic orbitals of the electron in a hydrogen atom at different energy levels. The probability of finding the electron is given by the color, as shown in the key at upper right.
3D views of some hydrogen-like atomic orbitals showing probability density and phase (g orbitals and higher are not shown)
Animation of continuously varying superpositions between the p_1 and the p_x orbitals. Note that this animation does not utilize the Condon–Shortley phase convention.
Transparent cloud view of a computed 6s (n = 6, ℓ = 0, m = 0) hydrogen orbital. The s orbitals, though spherically symmetric, have radially placed wave-nodes for n > 1. Only s orbitals invariably have a center anti-node; the other types never do.
Experimentally imaged 1s and 2p core-electron orbitals of Sr, including the effects of atomic thermal vibration and excitation broadening, retrieved from energy dispersive x-ray spectroscopy (EDX) in scanning transmission electron microscopy (STEM).