# Wavelength in an electron transition

1. May 4, 2009

### elephantorz

1. Is a 4p -> 4s transition allowed in sodium? If so, what is the wavelength? If not, why not? (Z = 11 for sodium)

2. $$\Delta$$l = |l2 - l1| = 1
That is for the first question, in which case it is allowed, hence |0-1| = |-1| = 1, and meets the requirements for the equation.

The second part is what I don't understand because I used these equations:
$$E_{n}$$ = $$\frac{-13.60}{n^{2}}$$eV
n = 1, 2, 3, ...

Next I used:
$$\Delta$$E$$_{atom}$$ = E$$_{1}$$ - E$$_{2}$$ = 0

Meaning, I get zero for this because of the repeating n = 4, then 4$$^{2}$$ which = 16 and therefore I have an issue here I do not know how to solve after pondering.

The third equation I must use is:
$$\lambda$$ = 1240 eV nm / $$\Delta$$E

But I am not there yet....

3. As you can see my attempt is either erroneous or there is some sort of lone energy I am not aware of, by the way, the answer to this is:

Yes; 2.21 $$\mu$$m

Thank you.

2. May 4, 2009

### nickjer

Ummm... Are you sure it is 4p to 4s? Double check what is written.

3. May 4, 2009

### elephantorz

I did, three times...I guess I will just have to lose points for this.

4. May 4, 2009

### nickjer

Is there a table in your book of the orbital dependence of the energy in sodium?

5. May 4, 2009

### nickjer

Here is an equation that uses different effective nuclear charges depending on the orbital quantum number:

http://physics.wm.edu/~inovikova/phys251/manual/naspec.pdf [Broken]

Last edited by a moderator: May 4, 2017