(I) Atomic orbital is the wave functionψ of an electron in an atom. All the acceptable solutions of SWE are called Eigen functions.(II) (n+l) value of 3d=5, 4p=5, 5s=5 ….but ‘n’ value in 3d < 4p < 5s;     (n+l) value of 4d=6;  Thus    Energy of 3d < 4p < 5s < 4d ;