Why do electrons enter the 4s orbital before entering the 3d orbital?

because the 3d orbital is at a lower energy level

because both the 4s and 3d orbitals are at the same energy level

because the 4s orbital is at a lower energy level

because the 4s orbital is at a higher energy level

i think its c. let me know if you make a 100 on plato.

So, a basic principle of the Universe is that particles WILL ALWAYS ENTER THE STATE OF LOWEST ENERGY. Because there are already so many electrons in the 3rd energy level, it jumps to the 4s level because there is less energy in the 4s level (because even though it's further out, there aren't that many electrons repelling it) — so it jumps to the place with lowest energy.

Hope this evaluation helps you!!