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Particle in a box and electron excitation

  1. Mar 8, 2014 #1
    1. The problem statement, all variables and given/known data
    Hello everyone, I have a question from a practice exam I can't seem to figure out.

    1. A Ca atom (atomic number = 20) is in the ground state. Light is shined on the atom, exciting the most energetic electron. Which of the following are possible quantum numbers (n,l,m) of this excited electron? Don't worry about spin.
    (a) (4, 0, 0)
    (b) (4, 1, -1), (4, 1, 0) and (4, 1, 1)
    (c) (5, 2, +1) and (5, 2, -1)
    (d) all of the above
    (e) none of the above

    2. Relevant equations
    See below

    3. The attempt at a solution

    1. I eliminated a) because the (4,0,0) state would be the 4s state, which is where the valence electrons are already located. Now, I am confused about why this electron cannot be promoted to the n=5 state. If enough energy is added, could it not go this state? Does have to do with the fact that we add a d orbital when we have (5,2,1)?

  2. jcsd
  3. Mar 9, 2014 #2


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    2017 Award

    Staff: Mentor

    There is a rule about spin that makes (5,2,+-1) very unlikely.
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