What is the electronic configuration?

Electron configurations of atoms follow a standard notation in which all electron-containing atomic subshells (with the number of electrons they hold written in superscript) are placed in a sequence.

For example, the electron configuration of sodium is 1s22s22p63s1.

Orbitals s, p, d, and f are the four chief nuclear orbitals. These orbitals ought to be filled by the number of electrons and the energy level of the orbital. We can arrange the four orbitals by their energy level as s < p < d < f.

As indicated by Aufbau’s principle the most reduced energy orbital ought to be filled first.

The s orbital can get two electrons while p, d and f orbitals can hold 6, 10 and 14 electrons separately.

Generally, the electronic configuration of these elements is (n-1) d 1–10ns 1–2. The (n–1) remains for the inward d orbitals which may have one to ten electrons and the peripheral ns orbital may have one or two electrons.