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In all the sites I have searched, shielding effect has been defined as the reduction of the nuclear attraction upon the outer electron/electrons, due to the core electrons that repulse the outer electron.

So, is the shielding effect specifically defined for outer shell electrons? Can't the shielding effect be defined for inner shell electrons?

If it can be defined, do the electrons in outer shells than that shell have any impact on the shielding effect?(They too must repulse the electron in the inner shell, possibly helping the nuclear attraction) If not, why?

Can someone help me out? Tks

SNB
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2 Answers2

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Generally, inner electrons shield outer electrons. In order to shield you have to be closer to the nucleus, but it's harder for an electron in a higher energy orbital to be closer to the nucleus than an electron in a lower energy orbital. Therefore the shielding effect from inner on outer is a lot more pronounced than outer on inner.

EDIT (after better understanding of OP's question): One thing to remember is that the inner electron can be on the same side of the nucleus as the outer electron, or it can be on the other side of the nucleus as the outer electron. In one case, the inner electron is being pushed towards the nucleus but the other case results in the inner electron being pushed away from the nucleus. A hand-wavy application of Gauss' Theorem suggests that these effects might cancel out over time. So, the net effect is that the outer electrons have minimal impact on the inner electrons. This argument fails if the outer electrons have greater nuclear penetration, but that doesn't happen by definition.

Zhe
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  • The question poster probably meant that the outer shell electrons will repel the inner shell electrons towards the nucleus, thus strengthening the attraction. – DHMO Oct 10 '16 at 14:03
  • Yes,he is is asking exactly same – Vidyanshu Mishra Oct 10 '16 at 14:09
  • @DHMO My sense is that that wouldn't be the case. We're dealing with an electron density (yes, it's going to be altered by the positions of the other electrons). Even though the distribution isn't spherical, I would posit that Gauss' theorem would say that the impact on the inner electrons is minimized on average over time. – Zhe Oct 10 '16 at 18:31
  • @Zhe can you explain your comment further? I feel that it might clear up my confusion, Pls keep it as simple as possible – SNB Oct 31 '16 at 13:04
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    If you consider a spherical shell of charge, what is the net electric field anywhere inside the sphere? Zero. In other words, the time averaged effect of outer electrons on inner electrons probably cancels out. This is probably grossly oversimplified, but from a purely physical perspective, I think it makes sense that the outer electrons have minimal effect on the inner ones. One other way to think about it is, when the outer electron pushes the inner electron closer to the nucleus, what happens when the outer electron ends up on the other side of the nucleus? – Zhe Oct 31 '16 at 13:44
  • Much clearer now, :) But, what do you mean by "what happens when the outer electron ends up on the other side of the nucleus?" – SNB Nov 01 '16 at 19:05
  • If that's the case, isn't it repelling the inner electron away from the nucleus? – Zhe Nov 01 '16 at 20:33
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The shielding effect describes the attraction between an electron and the nucleus in any atom with more than one electron shell. Shielding effect can be defined as a reduction in the nuclear charge on the electron cloud, due to a difference in the attraction forces of the electrons on the nucleus. You may also have heard of screening effect,these two are same.

Since the shielding effect is reducing the nuclear charge on the outer electrons,the net charge experienced by outer electron is called effective nuclear charge.

If you look at the formula of effective nuclear charge,you will see that Z*= Z-S {Where Z is the number of protons in the nucleus (atomic number) and S is the average number of electrons between the nucleus and the electron in question }

So it is evident that not only valence electrons but inner electrons experience shielding effect too but for inner electrons, shielding effect is less(a quick look to formula will clear it to you).

Now your next question is Do the electrons in outer shells than that shell have any impact on the shielding effect? the answer is NO

According to wikipedia(as shown in the image) electron in the higher energy levels do not contribute in anyway to sheilding effect.

Vidyanshu Mishra
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  • Nicely explained, but do you have any argument as to why outer electrons don't have any impact on the shielding effect? – SNB Nov 03 '16 at 18:14