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Hard Chem/Physics Question

  • #1

Homework Statement


In the equation for the bohr model of the atom, what is the n value for Li2+ ion?


Homework Equations


E = -2.178 x 10^-18J(z^2/n^2)


The Attempt at a Solution



Since it is Li2+ that means it has 1 electron. So z = 1. Now I have an equation with 2 variables (impossible to solve).

I dont know what E is and I have to find n. Does anyone have any idea on how to do this?
 

Answers and Replies

  • #2
3,740
417
z is the charge of the nucleus and is not 1 for Li.
For the rest, it may help to post the complete text of the problem.
 
  • #3
z is the charge of the nucleus and is not 1 for Li.
For the rest, it may help to post the complete text of the problem.
It's Li2+ not Li. And this is the complete text of the problem.....
 
  • #4
3,740
417
It does not matter. The charge of the nucleus is 3e for Li, Li+, Li2+.
So z=3.

But n can take any value so the question does not seem to make sense.
 
  • #5
IF the question is instead: In the equation for the bohr model of the atom, what is the z value for Li2+ ion?


Does this make more sense?
 
  • #6
DrClaude
Mentor
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IF the question is instead: In the equation for the bohr model of the atom, what is the z value for Li2+ ion?


Does this make more sense?
Yes.
 
  • #7
Yes.
Well isn't there still three unknown variables Energy and n value and z value?
 
  • #8
Borek
Mentor
28,401
2,800
But you are not asked to find all three, just to tell what (most likely) Z is.

As worded question doesn't make sense, unless it asks for Z, not n.
 
  • #9
662
307
Well isn't there still three unknown variables Energy and n value and z value?
What is Z? What does it mean? What is Z for lithium?
(yay! 200th post)
 
  • #10
The question exactly as it appears word for word is: In the equation for the Bohr model of the atom, what is the Z value for Li2+ ion?

I am still unsure of how to go about this question. Which equation should I use?
 
  • #11
DrClaude
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The question exactly as it appears word for word is: In the equation for the Bohr model of the atom, what is the Z value for Li2+ ion?

I am still unsure of how to go about this question. Which equation should I use?
You had the right equation in the OP. Go back in your notes/textbook and find what the ##Z## stands for.
 
  • #12
You had the right equation in the OP. Go back in your notes/textbook and find what the ##Z## stands for.
it stands for nuclear charge.
 
  • #13
Borek
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And what is nuclear charge for lithium?
 
  • #14
And what is nuclear charge for lithium?
It is +3. So there is no need to use the equation for this problem? Seems more challenging than that.
 
  • #15
Borek
Mentor
28,401
2,800
No, it is as simple as that. You were making it more difficult than it is from the very beginning.
 

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