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How many electrons can the outermost shell hold? 32 or 8?

  1. Jan 7, 2013 #1
    In this physics textbook, in the part where it is introducing atoms and in particular, electron shells. it says:

    "the first and inner most shell has a capacity for 2 electrons, the outermost shell has a capacity for 32 electrons"

    I thought the outermost shell always had a maximum capacity of 8.

    Is this not talking about the valence shell?

    or is there some cases where it could have a whole 32 and if so, why then does the arrow diagram (for electron configuration) give the 7th shell only s and p which would hold a maximum of 8?
  2. jcsd
  3. Jan 7, 2013 #2


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    hi ihaveabutt! :smile:
    no, the L (second) shell has a maximum of 8 …

    2 in the s sub-shell, and 6 in the p sub-shell​

    the sub-shells have 1, 3, 5, 7, 9 … orbits, multiplied by 2 for spin, making 2, 6, 10, 14, 18 …

    so the N (fourth) shell has a maximum of 2 + 6 + 10 + 14 = 32 electrons :wink:

    see http://en.wikipedia.org/wiki/Electron_shell#Number_of_electrons_in_each_shell
    No known element has more than 32 electrons in any one shell. This is because the subshells are filled according to the Aufbau principle. The first elements to have more than 32 electrons in one shell would belong to the g-block of period 8 of the periodic table. These elements would have some electrons in their 5g subshell and thus have more than 32 electrons in the O shell (fifth principal shell).​
  4. Jan 8, 2013 #3
    So how many electrons maximum for the (outermost) 7th shell?
  5. Jan 8, 2013 #4


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    how many do you think? :wink:
  6. Jan 9, 2013 #5
    8, but the book says 32.
  7. Jan 9, 2013 #6
    the answer is 32 for N = 4.

    The answer is 8 for N = 2: 2 in the 2s orbital, 6 in the 2p orbitals.
  8. Jan 9, 2013 #7


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    It depends on what you mean by shell. If you mean "all orbitals with the same value of the principal quantum number" - number of electrons is much higher. In general, nth shell holds up to 2n2 electrons on all subshells (orbitals - s, p, d, f...). Doesn't mean we know elements with 98 electrons on Q shell, that's just a theoretical number, but it is not clear whether the book refers to theory, or existing cases.
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