What Do Quantum Numbers Describe?

Quantum numbers describe the pathway, movement and designated orbitals of electrons in atoms. There are a total of four quantum numbers whose values describe the characteristics of the electrons in an atom and help to determine factors such as an element's atomic radius and ionization energy. The four quantum number values describe in detail the traits of an electron based on its spin, orbital, subshell and level.

The principal quantum number specifies the principal electron shell. It represents the most probable distance for an electron to be found from the atom's nucleus and provides an indication of the size of the atom. The orbital angular momentum quantum number describes the electron's angular distribution, and therefore the orbital shape. The magnetic quantum number indicates the orientation and number of electron orbitals within a subshell. The electron spin quantum number specifies the direction of an electron's spin and determines whether or not the atom can generate a magnetic field.

Taken together, the four quantum numbers provide information relating to the size, shape, number and orientation of an atom's electron orbitals, along with the directions in which each electron is spinning. In addition to helping to determine an atom's chemical properties, these values provide a means by which an atom's electron orbitals can be graphed. No two electrons within an atom will have the same set of quantum number values, and an electron's unique set of four values helps to determine its probable location.