For a mutielectron atom, the maximum of 2p-orbital in radial probability distribution graph is nearer the nucleus than that of 2s-orbital . Therefore, 2p-orbital should be closer to the nucleus and lower in energy than 2s-orbital. But 2s-orbital has lower energy than 2p-orbital. Explain.

For a mutielectron atom, the maximum of 2p-orbital in radial probabili

1.	For a mutielectron atom, the maximum of 2p-orbital in radial probability distribution graph is nearer the nucleus than that of 2s-orbital . Therefore, 2p-orbital should be closer to the nucleus and lower in energy than 2s-orbital. But 2s-orbital has lower energy than 2p-orbital. Explain.
Answer» Solution :The radial probability DISTRIBUTION graphs for 2s - and 2p- orbitals are shown below: It is clear from the figure that in case of 2s - orbital, there is a small additional PEAK or lamp. This indicates that a 2s-electron spends some of its time NEAR the nucleus. In other words, 2s-electron penetrates the `1s^2` - core (or K-shell, shown shaded in the figure). Due to penetration, a 2s- electron gets less shielding from other electrons and therefore, feels more nuclear charge. As a result, a 2s-electron is ATTRACTED more strongly by the nucleus than a 2p - electron. THUS, 2s has lower energy than a 2p - electron.