• Support PF! Buy your school textbooks, materials and every day products Here!

Energy levels

  • Thread starter Spruance
  • Start date
  • #1
33
0
The diagram shows some of the energy levels of an electron in a mercury atom. Level Q represents the lowest possible energy level.

bilde.png


(a)Explain why a line spectrum results from an atom with such energy levels.

(b) Calculate the energy change in joules when the electron moves from level P to level Q and determine the wavelength of the spectral line associated with this transition.

(c)Explain what is likely to happen if a moving electron of energy 7.0eV collides with an isolated mercury atom in the ground state.

(d)Explain what is likely to happen if a photon, also of energy 7.0eV were to be incident on the atom.

Planck’s constant = 6.6 x 10-34 Js,
speed of light = 3.0 x 108m/s,
charge on an electron = 1.6 x 10 -19 C

Thanks in advance
 

Answers and Replies

  • #2
33
0
I have at least tried to solve b)

-10,4 - (-5,5) = -4,9 eV = -7,84 * 10^-19J


f = E/h = (- 7.84 * 10^-19)/(6.63 * 10^-34) = - 1.18 * 10^15

lamba = (3 * 10^8)/(-1.18 * 10^15) = - 2.54 * 10^-7
 
  • #3
33
0
Have I done something wrong?
 
  • #4
Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,622
6
Spruance said:
I have at least tried to solve b)

-10,4 - (-5,5) = -4,9 eV = -7,84 * 10^-19J


f = E/h = (- 7.84 * 10^-19)/(6.63 * 10^-34) = - 1.18 * 10^15

lamba = (3 * 10^8)/(-1.18 * 10^15) = - 2.54 * 10^-7
Nope, this looks correct to me.

~H
 
  • #5
33
0
Hi

1) is not that important, I can always find some information on internet on it.

However, I didn't find any information in my textbook on c) and d). Anyone able (wanting? ...) to help me out?
 
Last edited:
  • #6
Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,622
6
Think in terms of 'if the electron / photon collides with an electron from a mercury nucleous'. With electron-electron collisions, the collision can either be elastic or inelastic. With a photon, all the energy is always absorbed by the electron. What happens if an electron gains energy?

~H
 
  • #7
33
0
I'm not completely sure
 
  • #8
Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,622
6
Spruance said:
I'm not completely sure
Think about energy levels, excitation....

~H
 
  • #9
33
0
I believe that the mercury atom would be excitated if it collides with a moving electron.
 
  • #10
Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,622
6
Spruance said:
I believe that the mercury atom would be excitated if it collides with a moving electron.
You would need to consider the energy of the electron, in relation to the energy levels of the mercury atom.

~H
 
  • #11
33
0
I don't think the mercury atom would be ionized
 
  • #12
Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,622
6
Spruance said:
I don't think the mercury atom would be ionized
No it wouldn't, what I'm getting at is you should make reference to the energy of the electron / photon in your asnwer and compare it to the energy levels. Excitation is a key word you should use.

~H
 
  • #13
33
0
10.4 - 7 = 3.4 eV
 
  • #14
Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,622
6
Spruance said:
10.4 - 7 = 3.4 eV
Correct, so it would be excited to the -3.7eV energy level.

~H
 
  • #15
33
0
Thanks

What would then happen in d?
 
  • #16
Hootenanny
Staff Emeritus
Science Advisor
Gold Member
9,622
6
As, I stated previously;

Hootenanny said:
With a photon, all the energy is always absorbed by the electron. What happens if an electron gains energy?

~H
 

Related Threads for: Energy levels

  • Last Post
Replies
2
Views
12K
  • Last Post
Replies
9
Views
3K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
4
Views
6K
  • Last Post
Replies
1
Views
3K
  • Last Post
Replies
3
Views
1K
  • Last Post
Replies
4
Views
7K
Top