Answer:
Please see the attached picture.
Explanation:
For subshell s, there is only 1 orbital hence 1 square is drawn. For subshell d, there are 5 orbitals hence 5 squares are drawn.
Period is the row number in the periodic table.
Note that there are some deviations from the aufbau principle (Electrons fill orbits of lowest sub energy level to capacity before filling orbitals of higher sub energy levels). For the first row of transition elements, chromium and copper deviate from Aufbau principle. Hence their electronic configuration does not follow the format.
