system
Given the following post, respond as if you're commenting on Reddit:
human
Why does orbital penetration reduce the energy of an orbital?

I've read that by approaching the nucleus, the electrons lose energy. So i'm guessing that the 2s orbital is lower in energy than 2p since it is more penetrating, likewise for how 1s is lower energy than 2s. I would like to think this has something to do with Coulomb's Law but I'm not too sure why or how electrons lose energy near the nucleus?
gpt
In a 1 electron system, the energy of 2s and 2p is identical. However, in a multielectron system the 2s is slightly lower in energy. The attraction between the 2p electrons and the nucleus is screened by the 1s electrons, i.e. the negative charge of the 1s electron cancels out some of the positive charge from the nucleus, so the 2p electron feels less attractive force. Note that this only happens because the 1s electron is in between the nucleus and the 2p electron. The 2s electron, on the other hand, has some orbital density very close to the nucleus, so it is less affected by the screening effect of the 1s electron.