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TO ye chem people out there;help out a chem-retard for 1sec

tidal822tidal822 Registered User Posts: 182 Junior Member
edited November 2005 in High School Life
ok, im using CC to learn chemistry. lame , but necessary.

regarding periodic trends..

whats the 'shielding effect'?
is it that the atom just gets fatter/bigger because its getting more valence orbitals filled as you go along the periodic table?

and to clarify, z effect is just atomic#-#electrons so you get the idea that the inner electrons experience a greater net attration while the outermost electrons experience a smaller attraction because the negative charges of the inside electrons counter the nucleus' positive charge - right?

Post edited by tidal822 on

Replies to: TO ye chem people out there;help out a chem-retard for 1sec

  • tidal822tidal822 Registered User Posts: 182 Junior Member
    i know cc ppl have to be good at chem, i know it
  • pianoking7pianoking7 Registered User Posts: 287 Junior Member
    I usually give physics help, but let me try this out.

    You pretty much have it right. The electrons around the nucleus are attracted, this happens in every atom. However, now you have a whole bunch of electrons, and they are slightly farther away from the nucleus. Moreover, now there are other electrons being attracted by the nucleus and at the same time pushing the many "outer" electrons away.

    This mainly occurs in transition metals (the ones in the middle of the periodic table).

    It's useful because it helps us understand why the d and f orbitals look so weird (compared to the s and p).
  • pyromanpyroman Registered User Posts: 301 Junior Member
    I really dont know what the "shielding effect" is but what i do know:

    atomic radii decrease as you go from left to right along the periodic table and increase as you go down. The reason for it decreasing when you go from left to right is that there are more electrons and protons, the attraction between the outer electrons and the nucleus is thus greater making the atom smaller. On the other hand, if you go down the table since you are adding a whole new level of electrons the radius of the atoms get bigger. Im not really sure if I answered your question.

    I dont know much about this z effect your talking about so i will leave someone else to explain that.
  • megaman123megaman123 Registered User Posts: 2,189 Senior Member
    shielding effect, let me see if I can remember ( note: I'm much more of a physics guys...so Im sorry if I mess up). Electron shielding is basically the aspect that as more electrons are added to the atom each time the pull of the nucleus on the outer electrons is less, the outer electrons are shielded from the full attraction of the nucleus by the inner electrons, so less energy is required to take those electrons off..Oh god I suck so much at explaing, sorry :(
  • seifoseifo Registered User Posts: 162 Junior Member
    well basically to expound upon previous points.... its a fact that atomic radii increases as you go down the periodic table. this is becuase as more electron shells are added, each one is "shielded" more by the inner electrons and can greater resist the attarction of protons in the nucleus. hope that helps
  • heerothewizardheerothewizard Registered User Posts: 169 Junior Member
    to use the analogy we used in class (it's a quite rigorous honors chem class, but we have a lot of fun...after the teacher explained shielding, one of our students explained it like this:)

    You have a piece of cake. Mmm. cake. The cake is the nucleus. You are an electron. you want to GET TO THAT CAKE and eat it. But wait! You see some dirt on the cake. You still want to eat the cake, it still looks tasty...but not so much as before.

    Basically: The nucleus's + charge attracts electrons with - charges. The charge "felt" by valence electrons is called Effective Nuclear Charge, because it is dampened by shielding. Shielding occurs when there are one or more electron shells (the dirt) between the nucleus and the valence electrons. The more levels in between the nucleus and the valence electrons, the higher the shielding. Lots of shielding leads to a bigger atom because the valence electrons are not attracted as strongly (Effective Nuclear Charge) to the nucleus as the core electrons are, and therefore tend to spread out further from the nucleus.
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