# Multiple lines in H2 and Hg emission spectra

1. Nov 11, 2007

### hagopbul

I was doing a test about rydberg constants using H2 and Hg light spectrum

And in the spectrograph I found that H2 have three spectra and the Hg have 5 spectra
And I DON'T KNOW WHY H2 have 3 lines and Hg have 5 lines?????? (Scientifically).

I know it is the numbers of the electrons that determine the number of the spectrum lines but how exactly?????
Can any one help me plz:surprised

2. Nov 11, 2007

### Retsam

Well it is the number of possible transitions that determine the number of spectrum lines you will see, and also the energy supplied to the atoms. If for example we imagine an atom has 3 energy levels, then the possible electron transitions would be :

n3 => n1 5 J
n3 => n2 3 J
n2 => n1 2 J

These energy levels are not proper values i have just made them up for the example. I have noted next to them the energy difference between each pair of shells. So if we supply energy to the electrons in an atom they may be excited to say the n3 state then they have gained 5J of energy. Now the electron will dexcite at some random time and could make either the n3 to n2 transition which means it will emit light of energy 3J, or make the n3 to n1 transition and emit light of 5J. The frequency of light depends on the energy change in the transition.

f = E/h

Last edited: Nov 11, 2007