you notice about the number of lines in both spectra? Account for the difference using concepts from the quantum mechanical model of the atom: 3 marks)
Study the following emission spectra: (KICA) helium: krypton: What do you notice about the number of lines in both spectra? Account for the difference using concepts from the quantum mechanical model of the atom: 3 marks)
The Correct Answer and Explanation is:
Answer:
When comparing the emission spectra of helium and krypton, we notice that krypton has many more spectral lines than helium. This is because krypton has a more complex atomic structure than helium.
According to the quantum mechanical model of the atom, each element’s emission spectrum is produced when electrons absorb energy and move to higher energy levels (excited states). When the electrons return to lower energy levels, they release energy in the form of photons, which appear as spectral lines. The number of possible electronic transitions depends on the number of electrons and available energy levels within the atom.
Helium has only two electrons and its electron configuration is 1s². Because there are fewer electrons and fewer possible energy transitions, helium’s emission spectrum has relatively few lines.
In contrast, krypton has 36 electrons with the electron configuration [Ar] 3d¹⁰ 4s² 4p⁶. With many electrons occupying multiple energy levels and sublevels (s, p, d), krypton has a far greater number of possible electron transitions. Additionally, electron-electron interactions and sublevel splitting further increase the number of available energy transitions, leading to a much more complex and dense emission spectrum with many more spectral lines.
Thus, the greater number of lines in krypton’s emission spectrum can be explained by its larger number of electrons, greater number of energy levels, sublevels, and possible electronic transitions as described by the quantum mechanical model of the atom.
Expanded Explanation
The emission spectrum of an element is a direct result of the quantum mechanical nature of atoms. According to this model, electrons in an atom occupy specific energy levels or orbitals. These orbitals are defined by quantum numbers, which determine the size, shape, and energy of the electron’s probable location around the nucleus.
When an atom absorbs energy, its electrons become excited and jump to higher energy levels. These excited states are unstable, so the electrons eventually return to their ground state, releasing energy in the form of photons. The wavelength of these photons corresponds to the energy difference between the two levels involved in the transition, producing the lines observed in the emission spectrum.
Helium, with only two electrons, has a simple electron configuration of 1s². There are only a limited number of energy levels and possible transitions for these two electrons, so helium’s emission spectrum contains relatively few lines.
On the other hand, krypton, with 36 electrons, has a much more complex electron configuration: [Ar] 3d¹⁰ 4s² 4p⁶. The presence of multiple electrons in different energy sublevels (s, p, d) allows for a vast number of possible transitions as electrons move between the various available energy levels. Furthermore, interactions between electrons (electron repulsion and spin-orbit coupling) split energy levels even further (known as fine structure), adding to the number of possible transitions. This complexity results in krypton having a very rich and dense emission spectrum with many more lines than helium.
In summary, the difference in the number of lines in the spectra of helium and krypton is due to the number of electrons and the complexity of available transitions in each atom, as explained by the quantum mechanical model of the atom.
