What is an orbital?
Each of the actual or potential patterns of electron density which may be formed in an atom or molecule by one or more electrons, and can be represented as a wave function is an orbital.
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In quantum mechanics, an atomic orbital is a mathematical function that describes the wave-like behavior of either one electron or a pair of electrons in an atom.
Each shell is subdivided into subshells, which are made up of orbitals, each of which has electrons with different angular momentum. Each orbital in a shell has a characteristic shape, and is named by a letter. They are: s, p, d, and f. Within any particular shell, the energy of the orbitals depend on the angular momentum of orbitals s, p, d, and f in order of lowest to highest energy. No two orbitals have the same energy level.
The shapes of the first five atomic orbitals are: $1s$, $2s$, $2p_x$, $2p_y$, and $2p_z$. The two colors show the phase or sign of the wave function in each region. These are graphs of $ψ(x, y, z)$ functions 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.