The arrangement of electrons in the orbitals of an atom or molecule.
So basically the electronic configuration tells us which element is present in which groups, in which periods and in which block (s block, p block, d block and f block).
By knowing how many electrons are present in the shells, we can find the place of an element in the periodic table.
Q: Find the electronic configuration of aluminium?
#(1s^2)/"K" " " (2s^2,2p^6)/"L"" "(3s^2,3p^1)/"M"#
it must be present in group lllA (in Roman Numerals). or group 13. and in the last shell, we have a