Introduction to Quantum Physics
Written: November 2015
Type atom into Google images and many "facts" are gathered about the nature of the atom:
In the first place, electrons do not orbit the nucleus of an atom in the usual sense of the word. For any electron, a well-defined path it might follow around the nucleus is impossible to specify, for the more precisely one measures where an electron is, the less one can know about where it is going, and vice versa. In order to find out where an electron is, one must "shoot" a photon at it. Otherwise, one is in the dark, so to speak. The more energy a photon fired at the electron has, the more precisely one may know where the electron is. Alternatively, the less energetic the photon used, the wider the field of potential "electron locations" will be. But here's the problem. When an electron is hit with a photon, it absorbs the photon's energy, and is thus moved off of its original trajectory or path (in other words, the "where it is going" of the electron is changed). So, the more precisely one measures the position of an electron, the less one may know about where it is, or was, going. This is known as Heisenberg's uncertainty principle.
But you may still be thinking, "Just because we can't know what the orbit of an electron is doesn't mean that such an orbit doesn't exist." This is true, and a growing number of physicists and philosophers of science are making this same point. But the dominant interpretation of the uncertainty principle says that electrons, and other subatomic particles, literally do not have a defined position or velocity until those properties are observed. As such, we may only speak in terms of broad spaces, as opposed to points, when discussing the location of a subatomic particle. In other words, the electron is (in some sense) spread out over many different points until it is observed.
Secondly, electrons are, in fact, extremely small when compared with protons or neutrons. Most of the of the mass of an atom is taken up by the nucleus. As an aside, neutrons are slightly smaller than protons. This shouldn't be a difficult concept to grasp, for every planet in the solar system (the equivalent of the electron) is much, much smaller than the Sun (the equivalent of the nucleus).
Finally, electrons do not all orbit the nucleus at relatively the same distance. Each electron is part of an electron shell. And there are multiple electron shells, each at different distances from the nucleus. Because of this, some electrons are closer than others. The closer an electron is to the nucleus of an atom, the less energy it has. Inversely, the more energy it has, the further away. This is because there exists a force of attraction between the positively charged proton and the negatively charged electron. It takes energy for an electron to resist this force of attraction. As it looses energy, it "gives in" to the attraction and moves closer to the nucleus. In short, different electrons of an atom can be and are different distances from the nucleus of an atom, given the different levels of energy each electron possesses.
Type atom into Google images and many "facts" are gathered about the nature of the atom:
- Electrons, much like planets, orbit the nucleus of the atom.
- The constituents of an atom are all relatively the same size.
- All electrons orbit the nucleus from the same distance.
In the first place, electrons do not orbit the nucleus of an atom in the usual sense of the word. For any electron, a well-defined path it might follow around the nucleus is impossible to specify, for the more precisely one measures where an electron is, the less one can know about where it is going, and vice versa. In order to find out where an electron is, one must "shoot" a photon at it. Otherwise, one is in the dark, so to speak. The more energy a photon fired at the electron has, the more precisely one may know where the electron is. Alternatively, the less energetic the photon used, the wider the field of potential "electron locations" will be. But here's the problem. When an electron is hit with a photon, it absorbs the photon's energy, and is thus moved off of its original trajectory or path (in other words, the "where it is going" of the electron is changed). So, the more precisely one measures the position of an electron, the less one may know about where it is, or was, going. This is known as Heisenberg's uncertainty principle. But you may still be thinking, "Just because we can't know what the orbit of an electron is doesn't mean that such an orbit doesn't exist." This is true, and a growing number of physicists and philosophers of science are making this same point. But the dominant interpretation of the uncertainty principle says that electrons, and other subatomic particles, literally do not have a defined position or velocity until those properties are observed. As such, we may only speak in terms of broad spaces, as opposed to points, when discussing the location of a subatomic particle. In other words, the electron is (in some sense) spread out over many different points until it is observed.
Secondly, electrons are, in fact, extremely small when compared with protons or neutrons. Most of the of the mass of an atom is taken up by the nucleus. As an aside, neutrons are slightly smaller than protons. This shouldn't be a difficult concept to grasp, for every planet in the solar system (the equivalent of the electron) is much, much smaller than the Sun (the equivalent of the nucleus).
Finally, electrons do not all orbit the nucleus at relatively the same distance. Each electron is part of an electron shell. And there are multiple electron shells, each at different distances from the nucleus. Because of this, some electrons are closer than others. The closer an electron is to the nucleus of an atom, the less energy it has. Inversely, the more energy it has, the further away. This is because there exists a force of attraction between the positively charged proton and the negatively charged electron. It takes energy for an electron to resist this force of attraction. As it looses energy, it "gives in" to the attraction and moves closer to the nucleus. In short, different electrons of an atom can be and are different distances from the nucleus of an atom, given the different levels of energy each electron possesses.
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