Science or Fiction? S1 Episode 26
The ancient Greeks pondered the building blocks that make up our world. After much thought, it was decided that upon dividing an object many many times then what remained would be entities which could no longer be broken down. These were called atoms.
Originally, Greek philosophers saw the universe as one single entity in which all matter or substance was connected as a unitary whole. This was not unlike many other societies around the world. The first Greek philosopher to deviate from this line was Democritus. As an alternative to the beliefs of other philosophers, he suggested the world could be divided into distinct quantities called atomos, or atomon. These he described as small, solid objects for which no further division was possible and comprised all matter in the universe.
Democritus
Democritus reasoned that various properties of matter were the result of how the atomos in an object were connected or combined. Extending this theory, he suggested there were different varieties of atomos with different shapes, sizes, and masses. Democritus surmised that other characteristics, such as color and taste, were not intrinsic properties of the atomos themselves. Rather, such characteristics resulted from the various ways in which the atomos were assembled or connected. This breakthrough, without experiment mind you, described what we now call chemical elements. If we consider that our formalized scientific method did not exist back then, other than trial and error, what Democritus proposed was astonishingly ahead of its time!
As a physics major, I struggled to keep up with all the new information slung in my direction along with the intense mathematics claiming to prove it. I now find it strange how neither in nuclear physics, electrodynamics, nor quantum mechanics was there much discussion of the nuclear structure. Perhaps this was glossed over as none of my professors really knew themselves? It is fairly certain, from quantum mechanics, that the electrons are not buzzing around the heavier nucleus like planets. I’m still irritated at the widely shown diagrams of atomic nuclei which indicate precisely that – with elliptical tracks indicating the orbital paths. Nonetheless, we call the positions of electrons orbitals when they are merely our best guess as to where we might find them. Quantum mechanics only yields a cloud of probability or the most likely region where electrons might be located in their quantized energy states.
Prior to early breakthroughs in quantum mechanics, we had an incomplete periodic table of the elements and little idea as to the nature of atoms themselves. Based on chemical properties, the categorization of matter had progressed rapidly throughout the 19th Century. The isolation or discovery of the first subatomic particle – the electron – was made in 1897 by J.J. Thompson. After years in which physicists had played around with cathode ray tubes and much speculation as to what the rays were, Thomson improved upon an experiment of the German scientist Hertz who concluded there was no charge associated with this stream of particles. With a harder vacuum, Thomson managed to deflect them between oppositely charged plates. This is where the first crisis occurred. Just as their predecessors pondered what kept the Moon crashing to the Earth, these modern scientists speculated on the structure of the atom. An electron buzzing around a positively charged nucleus must inevitably crash into it. It was also J.J. Thompson who determined the mass of the electron and proposed the plum pudding model for the atom in which protons and electrons were jumbled together – the electrons interspersed rather like plumbs in a positively charged pudding. In 1909, Robert Millikan and Harvey Fletcher determined the charge of a single electron to within 6% of today’s accepted value.
J.J. Thompson with the diagram of a cathode ray tube deflecting an electron beam between two charged plates.
This is where the first discontinuity in our formal physics training occurs. Quantum mechanics gives an excellent rational proof for the behavior and energy levels of electrons – in those orbitals we talked about – but very little on how the nucleus is put together. For the remainder of undergraduate and graduate school physics, we were presented only with a nucleus consisting of protons and neutrons. Other mysterious mechanisms called the strong and weak nuclear force were said to bind neutral particles, unimaginatively called neutrons within a ball of positively charged protons. The mass of the proton is about 1800 times greater than that of the electron but charges are equal and opposite. We know that like charges repel very stronly just as North-North or South-South ends of two magnets repel.
So, how could a collection of protons numbering from two as in a Helium atom up to the highest atomic numbers above 90 be confined so closely together? We’re told that most of the space that an atom occupies is empty as shown by Ernest Rutheford’s gold foil experiments. That is, if the nucleus were the size of a ping-pong ball on the 50 yard line, then the nearest electrons would be at the edges of the stadium. This is extremely tight confinement for like positive charges. Imagine a set of baseballs separated by very strong compressed springs and this tells you something of the energy released in atomic fission. So we have the Strong Nuclear Force holding everything together which is exerted between protons and neutrons. It is said to be attractive for protons and neutrons only at about one femtometer -- 10 E-15 meters -- but repulsive at less than 0.7 meters. A force that is both attractive and repulsive depending on distance sounds fishy already. It simply doesn’t act like other forces we are familiar with that are either one or the other.
Even if this schizophrenic Strong Nuclear Force is legitimate, what then? Why is there an upper limit on the size of atomic nuclei? We should have incredibly dense materials far stronger than iron or uranium, should we not? It would seem all we need is to keep sprinkling more neutrons into the mix with this magical Strong Force to make everything stable. Certainly in the case of gravity, the more particles we add – each with their attractive force – the greater the size of the resulting object be it planet, star, or black hole. As stated earlier, in my training, there’s been no suggestion of what an atomic nucleus actually looks like. We know the shape and organization of molecular structures. We can even take images of them through atomic force microscopy or X-ray diffraction. The latter was how the structure of DNA was deduced and human strand consists of nearly 3 million nucleotides. We also know that neutrons consist of one proton and one electron. An isolated neutron will decay into a proton, an electron, and an anti-neutrino in around 15 minutes so they’re not particularly stable. What is it about existing inside of the nucleus that keeps them intact? And why are only certain isotopes or atoms with excess neutrons stable while others are not?
In the limited instruction regarding atomic nuclei we were told of the stability of the nucleus and various isotopes. Atomic nuclei will build and become stronger up to the vicinity of iron. In general, the number of protons matches the number of neutrons with a slight excess of the latter. The very heaviest elements tend to be less stable and over time will undergo radioactive decay or splitting into constituents tending toward iron from the other direction. Quite common in radioactive decay is the emission of a He-4 atom and one or more single neutrons. Some isotopes are stable while others are radioactive even in the lower mass elements such as carbon. Carbon-12 is stable while Carbon-13 is very short-lived. Carbon-14 has a half-life of about 5,700 years. Isotopes for each element seem to occur in relative quantities in nature depending on their half-lives. This is the current thinking and used for carbon dating in organics or uranium-lead dating of minerals. It was here that one instructor likened the heavy elements to be more loosely bound taking us back to Thompson’s plum pudding model.
Again, if we have this Strong Force, why are heavier nuclei reduced to jelly-like objects just ready to fly apart? Some theorists are revisiting the question of structure in the nucleus. The science of chemistry and materials has yielded a number of geometries for crystal structure in elements or molecules. Nearly any substance may be crystallized from water or salt to proteins such as DNA. A crystal is just the organization of molecules in a repeating structure such as cubic, rhombihedral, hexagonal, etc. I had to memorize 20 of them for one class. If a nucleus consists only of protons and neutrons packed into the tightest possible space, then there might be a logical for this to be done.
The prevailing science is that nuclei have no fixed form. However, a Structured Atomic Model or SAM has been proposed which likens nuclei analogous to rigid crystalline structures for molecules. The key building blocks are the proton and the neutron redefined as a combined proton-electron pair, PEP. In this way quantum effects such as the uncertainty principle are set aside in favor of the classical behavior of protons and electrons. Further, it is the rigid nature with only certain allowable structures for the nucleus which carry over to the arrangement of electrons and chemical behavior of the element. These would include valance and oxidation states as well as bond angles. Another tenet of SAM which borrows from solid state physics strives for structures with spherical dense packing of constituents, namely protons. The most basic element is one PEP plus one proton – comprising a deuteron. The simplest units are protons with associated electrons acting as a kind of glue. This principle works up to the element of Carbon which is octahedral. Essentially, SAM is using the classic Greek perfect forms or those which may be inset into a sphere with vertices intersecting that sphere.
The order of building blocks is as follows. First is the proton, then a PEP or deuterium, tritium, He-3, He-4, skipping the unstable 5 sphere configurations to Li-7, Beryllium-9, Beryllium-10, Boron-10, Boron-11, Boron-12, and Carbon-12. These building blocks are thought to have the closest packing possible and are therefore the most stable. Heavier elements consist of a core typically of Carbon-12 plus branches built of these blocks. The sub-section of a branch will end in a completed stable block before a new branch is begun – again to maintain the closest packing possible. Close packing makes sense as the bond between positive and negative elements is very strong. If the ends of all branches are capped with a neutral ending or the constituent which makes that portion non-reactive then the atom is an inert noble gas. These gases have 4, 20, 40, 84, 132 and 222 protons.
For elemental variations, SAM assumes a basic structural configuration or base isotope. These are stable requiring no added PEPs as defined in SAM or neutrons in current physics. Such a basic structure will generally offer unambiguous connection points for extraneous PEPs. When one or more of these sites become occupied, we have a new isotope. Configurations varies from one element to the next, trending in larger elements able to handle extra PEPs. But, keeping with the original concept, more densely packed arrangements are most favored. Nuclei most prone to transmutation will have a misplaced PEP in this model. In time, it will shift to its correct position, reflected by the corresponding energy. This behavior is consistent with the observed behavior of known nuclides. There is also consistency with the maximum number of isotopes determined by available connection sites. For example, for carbon SAM yields a maximum number of 8 additional PEPs, which is in accordance with the observation that carbon-20. Before reaching that number, alternate additions will result in a stable element.
There are many other possibilities to which the Structured Atom Model may be applied while many details are still to be worked out. I invite you to visit the website structuredatom.org which has served as an important source. One of the goals for SAM is in making more sense of chemistry and nuclear physics and making it more accessible to people at large. As I delve into many of the questions in physics I find an uncomfortable number of them bogged down in complex mathematics. I’m beginning to wonder if theorists, brilliant as many of them are, are not fooling themselves. When one goes deeper into the rabbit hole, I find that they have often hit dead ends of which we are not aware. I’m finding hand-waving arguments, kluged equations, and worse. We must be open to the idea that even subjects pursued for the last 75 years may have simpler and more tangible solutions. I still believe there is a lot of basic physics out there within access of lay people in their garages without the politics of high priced government grants or universities.
Science or Fiction? Is a podcast written and presented by science fiction author and physicist Michael James Scharen in conjunction with the website michaelsbookcorner.com. A new episode is released each Thursday. The podcast is available on Spotify, Audible, Apple Podcasts, Amazon Music, Amazon Alexa, Podcast Addict, Podcast Republic, Anchor.fm, YouTube and other outlets. A complementary e-book is available at https://michaelsbookcorner.com/signup.html or joining the mailing list.