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Atomic Spectra and Energy Levels

Posted: Thu Oct 19, 2017 10:31 pm
by Alex Nechaev 1I
When electrons jump from one energy level to the next (n=1 to n=2, for example), how do we know when the energy exerted or used will be a negative value? If it goes down an energy level, will that finding of the energy from that jump be negative? Or is it the opposite?

1.69

Posted: Thu Oct 19, 2017 10:45 pm
by Gabriela Carrillo 1B
I understand that in order to figure out which laser should be used we must calculate the energies and compare that to the work function of lithium, but I don't understand where the numbers being used to calculate the work function are coming from. Where did (2.93 eV) and (1.60218x10^-19 JeV^-1) come from??

Re: Atomic Spectra and Energy Levels

Posted: Fri Oct 20, 2017 12:01 am
by nathansalce 3e
When an electron drops down to a lower level, the atom loses energy in the form of electromagnetic radiation.
When an electron jumps up a level, the atom gains energy instead.
Whether its positive or negative can depend on the question being asked.
"What is the change in energy of the atom?" the answer would be negative if an electron went down, or it would be positive if the electron jumped up a level
"How much did energy did the atom lose?" Now you're looking at likely a positive value, yet indicating that this value was lost during the reaction.

I wouldn't worry too much about the sign, just read the question and answer accordingly.

Re: Atomic Spectra and Energy Levels

Posted: Wed Oct 25, 2017 10:21 am
by Michelle Nguyen 2L
(Replying to the post about 1.69) The number for the work function 2.93 eV is an experimentally calculated value that differs for different metals. The other number, 1.602x10^-19, is a conversion factor that can be found in the back of your book to convert eV to the SI unit Joules. Hope that helps!