Two possible electron configurations for an Li atom are shown here. (c) In the absence of an external magnetic field, can we say that one electron configuration has a lower energy than the other? If so, which one has the lowest energy?

Video transcript

Welcome back everyone in this example we're given the falling diagram with two probable electron configurations. For an unknown adam given as X we're told that if a strong magnetic field is absent, is there a difference in the energies of the two configurations and if yes, which one has the higher energy. Now we want to recall two concepts are first being our principal quantum number and then the second being are as well. Quantum number recall that our principal quantum number is represented by the symbol N. And it refers to our energy level of our atom and so we can see that our atom has a configuration that goes up to the second energy level in both cases. So we would say that our principal principal quantum number for both of these configurations is to in our azimuth quantum number we should recall is calculated as n minus one. And so two minus one would give us a call quantum number which we recall is represented by the symbol L. Which we would say is equal to zero as well as being equal to one. And so to be clear for our principal quantum number we would say and is equal to two for both configurations. And then for as a muslim quantum number, L is equal to zero and one when we say two minus two minus one here. So these values are the same for both of our configurations. Despite recognizing that in configuration B we have a downward spin of our electron. So we have different spin quantum numbers where we would say our spin quantum number here recall that that is represented by M. Sabas is equal to negative one half. Which is why we have a downward arrow representing our electron here and then for configuration A we have a spin quantum number equal to positive one half. Now we're comparing the energies between these two configurations and because their principle quantum number and as a mutual quantum number are the same for both configurations. We would say that there's no difference in energy and this is regardless of this magnetic field being absent or present, they're still going to have the same energy regardless if we have a magnetic field or not. And so for our final answer, we're going to say that there is no difference in energy Between the two configurations we would say because both configurations maintain the same principal quantum number and as a quantum number and as we stated, the presence of a magnetic field or not does not affect this equality and energy between these two configurations. So what's highlighted in yellow is going to be our final answer to complete this example. I hope that everything I reviewed was clear. If you have any questions, please leave them down below and I will see everyone in the next practice video