What is the ground-state electron configuration of a neutral atom of cobalt?
electrons always try to fill the lowest energy levels available.
Only two electrons can occupy one orbital because no two electrons can occupy the same space and spin.
the first energy level has only one orbital the 1 s 2 electrons.
The second energy level has four orbital the 2s and 2 p 8 electrons
The third energy level has four orbitals the 3 s 3 ps 8 electrons.
This makes a total of 18 leaving nine more electrons.
The next two electrons go into the the 4 s leaving 7.
The 4 s is of lower energy than the 3 Ds . The 4s is a spherical orbital with a simple electron pattern. The 3 d are a complex electron pattern that looks like a four leaf clover. which requires more energy than the 4s even though the 4s is a greater distance from the nucleus.
The last 7 electrons go into the five 3 d orbitals. Two of the three d orbitals have two electrons. the last three have only 1 electron.