Question 1.11

[Josh Ku 3H]

Question 1.11 asks:
In the spectrum of atomic hydrogen, several lines are generally classified together as belonging to a series (for example, Balmer series, Lyman series, Paschen series). What is common to the lines within a series that makes grouping them together logical?

And the solution was:
In each of these series, the principal quantum number for the lower energy level involved is the same for each absorption line.

I'm a little confused on the terminology that they are using... what do they mean by "principal quantum number" and "lower energy level" and how are they the same for each absorption line?

[Miya McLaughlin 2B]

I believe "principal quantum number" is referring to the energy levels; n=1, 2, . . . etc.

According to the textbook, each of the series(Balmer, Lyman, etc.) correspond to a certain final value of n. For example, when an electron jumps down from n=3 to n=2, the line of radiation given off is in the Balmer series. Then, if it jumps from n=4 to n=2, that line is also included in the Balmer series. It's that final "quantum number" (n=2) that determines which series it belongs too.

Then "lower energy level" refers to the lowest n value involved, for the Balmer series it's n=2. The other series have different lowest values of n. Page 7 of the textbook also has information on this topic that could be helpful.

[TiengTum2D]

It doesn't matter where the energy level it starts from, the only thing you need to watch out for is where the energy level goes to, which will tell you to which series the lines belong to. For example, Balmer series lower energy level is 2 while Lyman series lower energy level is 1.