Penetration

[Michael Le 2D]

The book in chapter 2.5 describes inner-shell electrons as having a "penetrating effect." This is also seen in question #2.37 which states that electrons in an s-orbital are more effective than those in other orbitals at shielding from the nuclear charger because an electron in an s-orbital can PENETRATE to the nucleus of the atom. What exactly does this entail?

[Vanessa A 3F]

I hope this website helps with its explanation of orbital penetration.
http://chemwiki.ucdavis.edu/?title=Phys ... enetration

I think the main idea is that the electron probability density for s-orbitals is greatest at the center of the orbital, which is at the nucleus.

[Will Tsai 3C]

In my understanding, "penetrating" the nucleus just means that the electron can get very close to the nucleus, but not actually going through it. Electrons in "s" orbitals can get much closer to the nucleus than the ones in the "p" orbitals.