Each orbit can hold a maximum of electrons, where n is number of orbit.
The electronic configuration of an element gives the distribution of electrons in each of the orbit.
The electronic configuration of an element(Bohr-bury Rules):
The electrons in an atom arranged by certain rules known as Bohr-bury rules.
The electrons revolved in fixed orbit around the nucleus of an atom.
The orbits are numbered from the center outward. The first orbit closest to the nucleus numbered as 1 and named it as K - shell, next is numbered as 2 and denoted as L - shell, the next with 3 as M - shell, 4 as N - shell and so on.
The maximum number of electrons in the outermost shell cannot be exceed 8 and in the second last shell 18, irrespective of the shell number.
It is not necessary that last orbit should be filled with electrons for the next orbit to start filling- a new orbit starts filling as soon as the last orbit get 8 electrons. (For example, maximum number of electrons in the 3d shell is 18, but the 4th shell starts filling as soon as 3rd shell has 8 electrons)