## Atomic Spectra and Energy Levels

Alex Nechaev 1I
Posts: 50
Joined: Fri Sep 29, 2017 7:04 am

### Atomic Spectra and Energy Levels

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?

Gabriela Carrillo 1B
Posts: 53
Joined: Fri Sep 29, 2017 7:04 am

### 1.69

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??

nathansalce 3e
Posts: 52
Joined: Thu Jul 27, 2017 3:01 am

### Re: Atomic Spectra and Energy Levels

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.

Michelle Nguyen 2L
Posts: 50
Joined: Fri Sep 29, 2017 7:03 am

### Re: Atomic Spectra and Energy Levels

(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!

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