Question

Why is the spectrum of helium different from that of hydrogen?

Answer 1

We know that in order to answer this question, we must first understand the Bohr model for hydrogen and hydrogen-like substances and also the concept of spectrum. Molecular spectra are detected when a molecule absorbs or emits electromagnetic radiation, causing a rise or reduction in energy. The nonclassical notion that electrons move in particular shells, or orbits, around the nucleus underpins Bohr's hydrogen model.

Complete answer:
The hydrogen emission spectrum is a spectrum formed by the emission of light by excited hydrogen atoms. The helium emission spectrum, on the other hand, is a spectrum formed by the emission of light by helium atoms in excited states. The main distinction between hydrogen and helium emission spectra is that the helium emission spectrum contains more lines than the hydrogen emission spectrum. It is mostly due to the fact that hydrogen contains one electron per atom, but helium has two electrons per atom.
Furthermore, there is a significant difference between hydrogen and helium emission spectra in that electron-electron repulsions have no effect on hydrogen emission spectra due to the presence of a single electron in the hydrogen atom, whereas electron-electron repulsions affect helium emission spectra due to the presence of two electrons.
The emission spectrum is characterized by a sequence of lines on a black backdrop. The hydrogen emission spectrum is produced here by the emission of light by hydrogen atoms in excited states. The helium emission spectrum is produced by the emission of light by helium atoms in excited states. The primary distinction between hydrogen and helium emission spectra is that the helium emission spectrum has more lines than the hydrogen emission spectrum.

Note:
It must be noted that the Bohr model explained the hydrogen atom and other single electron systems like $H{e^ + }$. Unfortunately, when applied to the spectra of more complicated atoms, it did not perform as well. Furthermore, the Bohr model provided no explanation for why certain lines are more intense than others or why some spectral lines break into numerous lines in the presence of a magnetic field (the Zeeman effect).