We did a lab in our grade 11 chemistry class using spectrometers to see spectroms of various gases when 500 volts were passed through the gas discharge tube. There are a few questions and i dont know how to answer these ones. Please help!

First one
-->Hydrogen has only 1 electron. However its emission spectrum exhibits 4 visible lines. Can you explain??

Hints to the first question: Recall the aluminum bohr diagram(empty energy levels still exist). Electron in a particular energy level possesses a certain amount of energy. An electron can absorb additional energy from energy sources. Electrons hold on to extra energy for a short time (10^-6 seconds).

My second question.
Suggest reasons for neons many spectral lines and why they arent in the same locations as those from hydrogen.

my third question.
Mercury showed only a few visible spectral lines despite the fact that it posses 80 electrons. explain..

If you can even answer just one of these questions you'll be helping me alot.. Thank you in advance for any help!!