Why does the helium spectrum have more lines than the hydrogen spectrum?

Answer 1

Does the questioner mean, "Why does the helium spectrum have more VISIBLE lines than hydrogen?"?

I am not sure how many lines (within as well as outside the visible spectrum) that there are in the spectrum of each of these elements. I don't think anybody has worked out the spectrum of helium from first principles though they have for hydrogen (find out about the Balmer and Lyman series).

To hazard a guess, I would think that, because helium has two electrons instead of hydrogen's one, there are many more energy levels they can have so the lines relating to each change of energy would be more bunched together, hence the greater the chance of them falling within the visible range.

Answer 2

Both hydrogen and helium will escape from Earth's gravitational pull (unlike Jupiter and Saturn that trap hydrogen and helium).

Most of our helium supply today is in the form 4He, and is a radioactive decay product recovered in conjunction with oil wells.

The reason that there is more Hydrogen in our atmosphere is that the vast majority of it is bound to Oxygen in the form of H2O, water.

Some water would probably escape from the atmosphere as water vapor, except that the upper atmosphere is very cold causing the water to condense and fall back to the surface... a process called the "cold trap".

As an inert gas, Helium is essentially non-reactive with other elements. And, it has a very low boiling point/melting point so the "cold trap" is ineffective with the helium gas. Thus, it exists as single, very light, molecules that can escape from the earth's gravitational pull.

Answer 3

This is because there are way more possible/likely electronic transition. The relaxation of an electron from an excited state to a lower/ground state is achieved through the emission of a energy in the form of light/UV/IR. The difference of the two states determines the colour of the emission line.

(delta)E=h/(lambda)