Which of the density maps most accurately represents the possible location of the electron in an atom of hydrogen according to the quantum theory of the atom?
We’ve been given four images labeled from (A) to (D). The density maps illustrate the electron cloud. The electron cloud describes the region of space around the nucleus of an atom where there is a probability of finding an electron. The large black dot in each of the diagrams represents the nucleus, and the smaller blue dots represent the electron density. The closer the blue dots are to each other, the greater the likelihood of finding an electron in that position. The density map in option (A) has circular regions of electron density. And between each of these regions, there is no electron density, so there would be no chance of finding an electron.
The density map is similar to the Bohr model of the atom, where electrons go around the nucleus in flat circular orbits. This model is quite outdated, and the question asks for the density map according to the quantum theory of the atom. As part of this theory, electrons have a range of possible positions. At any point in time, an electron may be closer to the nucleus or further away, not at fixed distances as suggested in option (A). For this reason, option (A) is not the answer to this question.
As well as the density map being in accordance with quantum theory, it needs to represent the possible location of the electron in an atom of hydrogen. The electron in an atom of hydrogen can be found in the 1s orbital, where an atomic orbital is a three-dimensional mathematical expression that describes part of the electron cloud and is the most likely location of an electron in an atom. The 1s orbital has a spherical shape. The negatively charged electron will be strongly attracted to the positively charged nucleus of the hydrogen atom. So it is more likely to be found near the nucleus.
The density map in option (B) appears to fit this criteria well. Overall, it has a circular shape, which can represent the spherical shape of the 1s orbital. Additionally, the dots get closer together the closer you are to the nucleus. This indicates that the chance of finding an electron increases as we approach the nucleus. So, it appears as though option (B) is the answer to this question. But to confirm, let’s look at options (C) and (D).
Option (C) does not have a circular density map, so it doesn’t represent the spherical 1s orbital. For this reason, option (C) cannot be the answer to this question. Option (D) does have a circular density map, but the electron density doesn’t increase upon approaching the nucleus. Instead, it has strange local patches of increased electron density. There is nothing to attract the electron besides the nucleus in an atom of hydrogen, so there is no reason for these regions to form. Thus, option (D) is not the answer to this question.
Therefore, the answer to the question “Which of the density maps most accurately represents the possible location of the electron in an atom of hydrogen according to the quantum theory of the atom?” is (B).