If the 3d and 4s bands overlap in a metal atom, what is the maximum number of electrons for this composite band

Answer: 12 electrons

If the 3d and 4s bands are superimposed on a metal atom, the maximum number of electrons for this band will be 12 electrons. Remember that in layer 10 you can enter up to 10 electrons in the orbitals that you have, while the s can enter 2, therefore the amount of electrons that will enter the set formed by both bands when superimposed will be 12 electrons