Which electrons have most energy?

[Sarah Fatkin 4I]

Hi Chemistry Community! I thought that the electrons closest to the nucleus (with lowest n-value / at ground state) had the lowest (most negative) energy, but I just saw this in the textbook: "...electron-electron repulsions cause the energy of a 2p-orbital to be higher than that of a 2s-orbital." Why is this? I know that they have the same n value, but isn't the s sub-shell closer to the nucleus? Thanks!

[jonathanjchang2E]

Yeah you're right. The electrons closest to the nucleus do have lower energy, which is why the electrons in the 2s orbital are lower in energy than the electrons in the 2p orbital. The electrons in the 2p orbital are shielded by the electrons in the 2s orbital, which cause the 2p orbital electrons to be further away from the nucleus than the 2s electrons.

[Simran Athwal-Dis 3A]

Hey there, I wanted to know how can I differentiate between excited states of an atom and ground states of an atom?

[Searra Harding 4I]

Yes the s sub shell is closer to the nucleus than the p sub shell, therefore it has a lower energy than p. The electrons in 2p are more excited than those in 2s.