The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons.
The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen-1, which is the only stable nuclide with no neutrons).
The electrons of an atom are bound to the nucleus by the electromagnetic force.
Likewise, a group of atoms can remain bound to each other by chemical bonds based on the same force, forming a molecule.
An atom containing an equal number of protons and electrons is electrically neutral, otherwise it is positively or negatively charged and is known as an ion.
An atom is classified according to the number of protons and neutrons in its nucleus:
the number of protons determines the chemical element, and
the number of neutrons determines the isotope of the element.
An illustration of the helium atom, depicting the nucleus (pink) and the electron cloud distribution (black).
The nucleus (upper right) in helium-4 is in reality spherically symmetric and closely resembles the electron cloud, although for more complicated nuclei this is not always the case.
The black bar is one angstrom (100 pm).
Unfortunately, there is a distinct lack of real science that supports the currently favoured Rutherford Model which claims the atom “consists of a dense central nucleus surrounded by a cloud of negatively charged electrons”.
In 1904 the state of the art atomic theory was based upon J. J. Thomson’s Plum Pudding Model which had negatively charged electrons dispersed in a sea of positive charge.
The physicist J. J. Thomson, through his work on cathode rays in 1897, discovered the electron, and concluded that they were a component of every atom.
Thus he overturned the belief that atoms are the indivisible, ultimate particles of matter.
Thomson postulated that the low mass, negatively charged electrons were distributed throughout the atom, possibly rotating in rings, with their charge balanced by the presence of a uniform sea of positive charge.
This later became known as the Plum Pudding Model.
A schematic presentation of the Plum Pudding Model of the atom.
In Thomson’s mathematical model the “corpuscles” (or modern electrons) were arranged non-randomly, in rotating rings.
Then, in 1909, Hans Geiger and Ernest Marsden [under the direction Rutherford] performed the Rutherford Gold Foil Experiment.
The gold foil experiment consisted of a series of tests in which positively charged alpha particles (helium nuclei) were fired at a very thin sheet of gold foil.
If Thomson’s Plum Pudding model was to be accurate, the big alpha particles should have passed through the gold foil with only a few minor deflections.
This is because the alpha particles are heavy and the charge in the “plum pudding model” is widely spread.
The results of the Rutherford Gold Foil Experiment were very much as expected although “a very small percentage of particles were deflected through angles much larger than 90 degrees” which caused some alpha particles to be “reflected back to the alpha source”.
Although many of the alpha particles did pass through as expected, many others were deflected at small angles while others were reflected back to the alpha source.
They observed that a very small percentage of particles were deflected through angles much larger than 90 degrees.
Rutherford interpreted the experimental results in a famous 1911 paper.
He was able to definitively reject J.J. Thomson’s plum pudding model of the atom, since none of Thomson’s negative “corpuscles” (i.e. electrons) contained enough charge or mass to deflect alphas strongly, nor did the diffuse positive “pudding” or cloudlike positive charge, in which the electrons were embedded in the plum pudding model.
Instead, Rutherford suggested that a large amount of the atom’s charge and mass is instead concentrated into a very physically small (as compared with the size of the atom) region, giving it a very high electric field.
Outside of this “central charge” (later termed the nucleus), he proposed that the atom was mostly empty space.
Although Rutherford’s model of the atom itself had a number of problems with electron charge placement and motion, which were only resolved following the development of quantum mechanics, the central conclusion from the Geiger–Marsden experiment, the existence of the nucleus, still holds.
Sadly, the observation that “a very small percentage of particles were deflected through angles much larger than 90 degrees” does not tell the observer what exactly caused the deflections and it does not demonstrate that the atom has “a minute massive centre, carrying a charge” [although that may be one theoretical possibility].
The Rutherford Model theorises that:
1) The “scattering backward must be the result of a single collision” and does not entertain any other possibilities, such as; back scattering resulting from multiple [incremental] collisions.
2) The atom has “a minute massive centre, carrying a charge” and does not entertain any other possibilities, such as; the atom is encased in a shell [or framework] that carries charge.
3) The “atom is mostly open space” and does not entertain any other possibilities such as; negatively charged electrons are dispersed in a sea of positive charge [which an alpha particle can easily transit – as per the Plum Pudding Model].
Perhaps the greatest conceptual problem associated with the Rutherford Model [where a spherical central nucleus is surrounded by a spherical electron cloud] is that the physical characteristics of this design makes the atom an extremely impractical building block.
Firstly, negatively charged electron clouds [and positive nuclei] mutually repel.
Secondly, the bonding area between spheres is a weak “point contact” where the spheres “kiss”.
Thirdly, spheres are difficult to stack in a gravity field especially when each sphere is surrounded by a repelling electron cloud.
Additionally, the one template fits all approach of the spherical atom in the Rutherford Model makes it extremely difficult to account for the huge variety of properties that differentiate individual elements and molecules.
The mainstream fudge is to magically append a wide variety of spacer bars [of unknown origin] to the spherical atom defined by the Rutherford Model.
Clearly, the design of the One Template Fits All Rutherford Atom is distinctly suboptimal.
Clearly, scientists have been obliged to creatively fudge workarounds for the dysfunctional One Template Fits All Rutherford Atom.
Clearly, all other advances in atomic theory [such as the 1916 Cubical Atomic Model] have been sidelined by the mainstream.
The cubical atom was an early atomic model in which electrons were positioned at the eight corners of a cube in a non-polar atom or molecule.
This theory was developed in 1902 by Gilbert N. Lewis and published in 1916 in the famous article “The Atom and the Molecule” and used to account for the phenomenon of valency.
Lewis’s theory was based on Abegg’s rule.
It was further developed in 1919 by Irving Langmuir as the cubical octet atom.
The real problem with the One Template Fits All Rutherford Atom is that the empirical evidence clearly falsifies the Rutherford Model.
The problem becomes apparent when scientists measure the “gaps” between atoms.
According to the Rutherford Model these “gaps” must represent the distance between atomic nuclei [and all other possible interpretations are ignored by the mainstream].
Obediently, scientists divide the measured “gaps” by two and deem the result to be the Atomic Radius of the element being measured.
Measuring these theoretical “gaps” is an advanced art form because the Rutherford Model does not include the wide variety of magical spacer bars that are required to explain the real world.
The radius of an atom is not a uniquely defined property and depends on the definition.
Data derived from other sources with different assumptions cannot be compared.
Unsurprisingly, the “empirical” Atomic Radii fail to reveal the steady, incremental growth of the Rutherford Atomic Nucleus as neutrons and protons are incorporated into the atom.
Unsurprisingly, even the fudged theoretical calculations fail to match “empirical” data.
What the “empirical” data does reveal is that there are six step changes in the Atomic Radii which indicates six different Atomic Shells are required to support all the combinations of electrons, protons and neutrons found in the Periodic Table.
The concept of atomic shells is further confirmed [and the Rutherford Model is falsified] when the atomic volume is plotted against Atomic Weight.
The atomic volume confirms there are atomic shells which become denser as additional electrons, protons and neutrons are incorporated into the framework of the atomic shell.
Conceptually, the atomic shell reflects the real world where an object can usually be identified by its exterior appearance. This implies an atomic shell is a framework that encapsulates a number of electrons and protons that are separated by dielectric neutrons.
A dielectric material (dielectric for short) is an electrical insulator that can be polarized by an applied electric field.
When a dielectric is placed in an electric field, electric charges do not flow through the material as they do in a conductor, but only slightly shift from their average equilibrium positions causing dielectric polarization.
Because of dielectric polarization, positive charges are displaced toward the field and negative charges shift in the opposite direction.
Conceptually, the framework of an atomic shell enables strong electrical bonding [without the need for “spacer bars”] by exposing the electrons and protons contained within the atomic framework.
Conceptually, a variety of atomic shell frameworks helps explain the multitude of physical properties [of matter] that are encountered in the real world.
Conceptually, a variety of atomic shell frameworks provides a robust set of building blocks that helps explain the variety of natural shapes encountered in the real world.
Unfortunately, until the mainstream accepts that the Rutherford Model has been falsified it is unlikely that much progress will be made in defining the characteristics of the six atomic shells found in the periodic table.
However, a good starting position might be the Platonic and Kepler–Poinsot polyhedrons.