Worth 20 pt plz answerwhy are the oldest parts of the ocean floor no older than about 200 million years old

Because of subduction, the plates constantly bump into and change each other. Even though the ocean is 4 billion years old, subduction constantly changes the bottom of the ocean. The oldest piece of sediment is only 180 million years old.. for now at least...

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.