Together, these four quantum numbers can be used to describe the location of an electron in Bohr's hydrogen atom. There is a fourth quantum number, called the spin magnetic quantum number (m s), which is not obtained from solving the Schrödinger equation. By solving the Schrödinger equation for the hydrogen atom, we obtain three quantum numbers, namely the principal quantum number (n), the orbital angular momentum quantum number ( l), and the magnetic quantum number (m l). The wavefunction is the solution to the Schrödinger equation. When assigning electrons to orbitals, we must follow a set of three rules: the Aufbau Principle, the Pauli-Exclusion Principle, and Hund's Rule. Hence, many of the rules that we use to describe the electron's address in the hydrogen atom can also be used in systems involving multiple electrons. In doing so, we obtain three quantum numbers (n, l,m l), which are the same as the ones obtained from solving the Schrödinger's equation for Bohr's hydrogen atom.
Under the orbital approximation, we let each electron occupy an orbital, which can be solved by a single wavefunction. The electron configuration is the standard notation used to describe the electronic structure of an atom.
