My doubt is why don't we write 4s orbital before 3d as it is lower in energy according to Aufbau's principle? (I'm getting this info from other sites that 3d comes before 4s in transition metals but I'm not pretty sure about this thing)
Further, why are 4p and 4d come directly after 4s? Should have 5s come before 4d according to Aufbau's Principle?
Please help me I'm very much confused