# Homework Help: Bohr Model

1. Dec 11, 2011

### ChiefKeeper92

Bohr Model
1. Assuming that the wavelengths of visible light lie between about 300nm and 700nm, what transitions in Li++ (hydrogenic lithium ions, Z=3) would be visible. Identify each transition by initial and final principal quantum number n. Also identify those transitions that are also seen in hydrogen (3->2, 4->2, 5->2 in hydrogen)

2. E=13.6eV*(Z^2)*((1/n)^2-(1/m)^2)
λ=1240/E

3. I ran through it but I keep getting the same wavelengths as hydrogen. I don't know what I'm doing wrong. Do I multiply n*Z on the bottom before I square it?

2. Dec 11, 2011

### ehild

What did you use for Z? Remember, the atomic number of Lithium is 3, and the nucleus of the Li++ ion has 3e charge.

ehild

3. Dec 11, 2011

### ChiefKeeper92

I used Z=3 but do I need to multiply Z by n and m?

4. Dec 11, 2011

### ehild

I do not understand you. You need to substitute different n-s and m-s into the formula. First evaluate the expression in the parentheses, (1/n2-1/m2). Then multiply the result by (13.6 * 9).

ehild