Video Transcript
Which diagram most closely represents Bohr’s electron shell model of the atom?
The scientist Niels Bohr suggested in his electron shell model of the atom that surrounding the nucleus, which contains protons and neutrons, negatively charged electrons are locked into orbits. His model showed that these orbits in which the electrons surrounded the nucleus were discrete energy levels and the amount of energy of the electrons on energy levels was dependent on the radius. So, for example, the energy of these two electrons on this first energy shell would be of lower energy than this electron farthest from the nucleus due to the difference in radii of the energy shells.
This model was hugely important as it explained line emission spectra. A line emission spectrum is a set of wavelengths of light emitted from an element when its electrons drop from a higher energy state to a lower energy state. For example, if a hydrogen atom were to have its electron excited and jump to the third energy shell, when this excited electron falls from the third energy shell to the second energy shell, a very specific wavelength of light would be emitted, producing a red color. Bohr’s model explained that because specific electron transitions resulted in specific wavelengths of light being emitted or absorbed, the energy levels in the atom are associated with discrete amounts of energy. While more work has since been done to reveal that this model is incomplete, it was an incredibly significant development in the journey of atomic theory.
Let’s now have a look at our answer choices. Answer choice (A) appears to match very closely what we have identified as Bohr’s electron shell model. It appears we have already found the correct answer. But let’s rule out answer choices (B), (C), (D), and (E) just to be sure.
Answer choice (B) resembles Thompson’s plum-pudding model, which suggested that negatively charged particles were embedded in a sea of positive charge. We can eliminate answer choice (B). Answer choice (C) looks like the plum-pudding model with positive and negative charges reversed. Answer choice (C) does not resemble any atomic model and can be eliminated. Answer choice (D) shows a dense, positive center with electrons orbiting it as planets in our solar system orbit the Sun. This model resembles Rutherford’s planetary model, which can also be called the nuclear model. We can eliminate answer choice (D). Finally, answer choice (E) shows a cube with electrons making up the corners of this cube. This model appears to represent Lewis’s cubic model of the atom. So we can eliminate answer choice (E).
Therefore, the diagram that most closely represents Bohr’s electron shell model of the atom is answer choice (A).
