Question on textbook 1E5

[Rainy Liu Ruoshui_2K]

The question says:
Electrons in an s-orbital are more effective than those in other orbitals at shielding other electrons from the nuclear charge because an electron in an s-orbital can penetrate to the nucleus of the atom.

The answer says this is correct. Can anyone help explain how an electron can 'penetrate to the nucleus'?

[Shivani Sakthi 1l]

The penetration ability of an electron is the ability of an electron within a specific subshell to move/penetrate within other shells and subshells to decrease in proximity to the nucleus. In other words, it is the ability of an electron to resist staying in its designated location in hopes to move closer to the nucleus, because opposite charges attract. Both the shell number (n), which indicates the distance of an electron from the nucleus, as well as the subshell, or the angular orbital momentum, impact penetration abilities. Electrons in orbitals with lower n values penetrate the nucleus more effectively because they are lower in distance from the nucleus, so the positive nuclear charge pulls more greatly on the electrons. Electrons in orbitals with higher l values, such as l=1, the p orbital, compared to l=0, the s orbital, have a higher angular orbital momentum that prevents it from approaching the nucleus, so they have lower penetration abilities because it is harder to approach the nucleus. This is why the s orbital, with l=1, can penetrate the nucleus.

To put this into context: The 2p orbital has a lower penetration ability than the 2s orbital because the 2s orbital is closer to the nucleus and has a lower angular orbital momentum, increasing the pull of the 2s electrons towards the nucleus.