What causes the atomic spectra of different elements to differ?

Question

we did an experiment about atomic spectra. we use a discharge tube of sodium. we found wavelenght for each colour.

Answer 1

The light you see comes from photons emitted when an electron drops from a higher-energy orbit to a lower-energy one. Quantum mechanics requires that the length of the orbit be an integral multiple of the wavelength of the electron's wavefunction. That means these orbit energy levels are discrete, and so the energy difference between the levels has a very specific value, and the photon emitted must have exactly that energy and therefore that frequency. Different elements will have different possible orbital energy levels, and therefore different emission spectra.