Principal quantum number

The positive integer quantum number n labels an atomic electron’s principal energy level and shell. It helps determine orbital energy and size.

Quantum number: A numerical label specifying a measurable aspect of a quantum system’s state. The principal quantum number is one of the labels used to specify an atomic electron’s state.
Hydrogen atom: The simplest atom, consisting of one proton and one electron. Its energy levels show the direct dependence of bound-state energy on n.
Electron configuration: A specification of how electrons occupy an atom’s available quantum states. The principal quantum number groups occupied states into shells.
Subshell: A subdivision of an electron shell distinguished by the orbital angular-momentum quantum number l. A shell with fixed n can contain several subshells with different orbital shapes and energies.
Atomic orbital: A quantum state of an electron in an atom, often represented by a spatial probability distribution. The principal quantum number helps set an orbital’s characteristic size and energy.
Bohr model: An early atomic model that assigns electrons discrete orbital energies and angular momenta. It introduced shell labels corresponding to discrete principal energy levels.
Aufbau principle: A rule of thumb for constructing electron configurations by filling lower-energy orbitals first. Shell and subshell energies indexed partly by n guide the filling order.
Fine structure: Small splittings of atomic spectral lines caused chiefly by relativistic and spin–orbit effects. It shows that energy levels can split even when a principal shell is specified.
Electron shell: A grouping of atomic electron states associated with the same principal quantum number. Shells are the energy-level groupings that n labels.
Rydberg formula: A formula that predicts wavelengths of spectral lines from transitions between atomic energy levels. For hydrogen, its level energies are indexed by the principal quantum number.

Linked from 15 pages