QuestionAtomic structure / penetration and shielding
Consider the following diagram regarding the radial distribution function for 2s and 2p orbitals :
Which one of the following statements is a correct conclusion drawn from the diagram given above ?
- (a) 2s electrons are less shielded than 2p electrons.
- (b) 2p electrons are less shielded than 2s electrons.
- (c) 2s and 2p orbitals have equal probability of closer approach to nucleus.
- (d) 2s orbital electron density is at a greater distance from nucleus than that of 2p orbital.
Answer: (a) 2s electrons are less shielded than 2p electrons.
The 2s curve has a small inner maximum very close to the nucleus, inside the main 2p maximum. So a 2s electron penetrates the inner core more and feels a larger Z_eff. Greater penetration means less shielding: 2s electrons are less shielded than 2p electrons → (a). Remember: penetration order s > p > d > f, hence energy order ns < np < nd < nf in many-electron atoms.