Question

The line spectrum of helium has many more lines in it than the line spectrum of hydrogen. Draw orbital energy diagrams for both H and He, showing all orbitals up through n = 3. Use these diagrams to explain why helium’s line spectrum is so much more complex. They should differ in more than just the number of electrons!

Answer 1

Spectral lines are the result of interaction between a quantum system (usually atoms, but sometimes molecules or atomic nuclei) and a single photon. When a photon has about the right amount of energy to allow a change in the energy state of the system (in the case of an atom this is usually an electron changing orbitals), the photon is absorbed. Then it will be spontaneously re-emitted, either in the same frequency as the original or in a cascade, where the sum of the energies of the photons emitted will be equal to the energy of the one absorbed (assuming the system returns to its original state). The direction and polarization of the new photons will, in general, correlate with those of the original photon.

In other words The spectral lines are the result of the Electrons around the atom. Electrons are directly proportional to the number of protons in an atom. Hydrogen has 1 proton and therefore has 1 electron. The more electrons an atom has the more spectral lines it is able to produce.