Posted by Brenda on .
a.) Caculate the energy of light emitted when an electron moves from n=2 to n=1 in the hydrogen atom.
b.) Caculate the energy of light emitted when an electron moves from n=4 to n=2 in the hydrogen atom.
c.) How many total different light energies can be emitted from an electron moving down from n=5?
I don't know the equation for a.) and b.), and I don't understand c.). Help please!

Chemistry 
DrBob222,
E= 2.180E18(1/n^2(1)  1/n^2(2))
R = 1.09737E7
n1 = 1 so n^2 = 1
n2 = 2 so n^2 = 1/2^2 = 1/4
For b the only difference is
n1 = 2 so n^2 = 4
n2 = 4 so n^2 = 16
For c draw a diagram of energy levels that will look something like this.
n = 5 
n = 4 
n = 3 
n = 2 
n = 1 
So an electron can move from
5 to 4;
5 to 3;
5 to 2;
5 to 1 and this results in 4 different energies being emitted.
After the 5 to 4, then the 4 can do the same thing; i.e.,
4 to 3;
4 to 2;
4 to 1; which results in 3 more energies being emitted.
Then the electron that goes from 5 to 3 can separately do
3 to 2; and
3 to 1; resulting in two more and finally, the one at 2 can do
2 to 1 resulting in 1 more. Add those together for the total. If I could draw a diagram on this site I could explain it much better.