Historical Models of the Atom
Leucippus' and Democritus' Atom
Our English word “atom” comes from a Greek word
“atomos” meaning the smallest unit of matter. Leucippus and
Democritus, Greek philosophers of the late 5th century BC, taught that
the smallest unit of matter, the atom, was irreducible and
indestructible. “They believed that everything in the universe
was composed of atoms.... There were an infinite number of atoms....
Atoms differed as to their size, shape, and perhaps their weight.”
Leucippus and Democritus came to their opinions
about atoms by means of deduction: They knew that materials on earth,
such as rocks, water or sand, are stable. For example, rocks don't just
appear and then disappear. The early Greek scientists also could see
that if they broke a piece of gold into two pieces, it was still gold
(same color, soft metal, etc.). But they asked, how small could a piece
of gold become by repeated breaking and still remain gold? They deduced
that when it became as small as a single atom, it would still be gold.
But if anyone could break that single atom into smaller pieces, the
gold atom would cease to exist. And we know that if there was anything
left, it certainly wouldn't be gold.
In 1897, J. J. Thomson showed by his famous experiment that there were
small charged particles; today we call these particles electrons. By
1904, Thomson “developed the picture of an atom as a sphere of
positive charge, occupying the whole volume of the atom, with electrons
embedded in it.” Thomson's atom was able to explain some chemical
properties of the many kinds of atoms known at this time (less than
100). The Thomson model of the atom had to be abandoned, however,
because new experiments showed that at least most of the positive
charge (from protons) was concentrated in the center of the atom, not
over the entire volume.
“In 1911 Rutherford put forward the hypotheses that the positive
charge of the atom was concentrated in a very small volume...within the
nucleus.” In this model, the electrons were scattered around the
volume of the atom outside the nucleus.
In 1913, Niels Bohr proposed a theory of the hydrogen atom (the most
simple of all atoms) consisting of one heavy proton in the center with
one lighter electron in orbit around the proton. Bohr supposed
- That electrons move in circular orbits around
the atomic nucleus.
- Only certain orbits are permitted.
- That in these permitted orbits, the electrons
would not radiate (would not create radio waves).
- That light of certain colors (and wavelengths)
would be created when the electron (of its own power) changed orbits.
These postulates were entirely arbitrary and even
violated the established laws of electricity and magnetism. In spite of
this, physicists still use the Bohr model (when it is convenient).
Parson's Magneton Theory of the
“By 1915, A. L. Parson knew that the Bohr model of the atom could
not be real, so he developed and even experimented on a model of the
atom where the electrons were not point-sized particles that orbit
around the atomic nucleus. In Parson's atom, the electrons in the
shells surrounding the nucleus were rings of charge (with the shape of
a toroid or donut). Since the electrostatic charge at the surface of
the these rings is rotating, each electron is a tiny magnet. In 1918,
Dr. H. Stanley Allen of the University of Edinburgh discussed the
arguments in favor of the ring electron, showing how it removed many
outstanding difficulties of other theories of the atom. In spite of its
superiority, Parson's magneton model of the atom did not become popular
(but a modern version, the Lucas model of the atom, has now been
De Broglie's Model of Matter:
“About 1924, Louis de Broglie proposed that all particles of
matter (from single atoms to large objects) moving at some velocity
would have the properties of a wave. Today, most physicists take this
farther and say that all material objects actually are waves until they
are measured or observed in some way. When this takes place, the wave
is said to collapse and turn into an object. An example of this notion
of reality is given by the famous Cornell physicist N. David Mermin who
says "We now know that moon is demonstrably not there when nobody
Schrodinger's Wave Model of the
“"In 1925, soon after de Broglie had put forward his ideas,
Schrodinger used them [to write] a wave equation to describe this new
mechanics of particles." Schrodinger's model of the atom is not a
physical model (where an object has size, shape and boundaries) but is
a mathematical model (an equation where objects are point particles.)
The equation is useful to predict some properties of objects (or
atoms), but is not able to describe the object (or atom) itself.
Dirac's Model of the Atom
“The Dirac model is an equation that includes imaginary numbers.
It is not an attempt to describe the objective reality of the physical
electron, but to predict the various levels of energy that the electron
may have at various times. There appears to be a serious problem with
the Dirac model which has the electrons orbiting the nucleus. Another
major assumption of the Dirac theory is that the statistical version of
quantum wave theory or quantum mechanics is valid. Unlike previous
quantum theories of the atom that used real numbers (such as the Bohr
model and Schrodinger model), the terms and imaginary numbers in
Dirac's equation do not correspond to measurable quantities.
Standard Model of Elementary
“The Standard Model of Elementary Particles is not a description
of the atom. However, we must mention it now because in modern theory,
atoms are not only waves, but when measured the atoms change into
objects composed of elementary particles. In modern physics, the
important components of the atoms are electrons, protons, and neutrons.
The Standard Model considers electrons to be true elementary particles,
either waves or point particles with inherent properties of mass,
magnetism, spin and stability. But in modern Quantum Theory, protons
are supposed to be composed of quarks; and neutrons are thought to be
composed of a different combination of quarks. Another important part
of the Standard Model is that forces between these elementary particles
are supposed to be carried by other particles that move back and force
randomly between the material particles:
- photons are supposed to be particles that
carry forces between electrons,
- mesons are supposed to be particles that carry
forces between protons and neutrons,
- gluons are supposed to be particles that carry
forces between the quarks (which are supposed to be inside protons and
Lucas Model of the Atom
“In 1996, while still a high school student, Joseph Lucas
introduced his model of the atom. In this model, electrons, protons and
neutrons are all based on Bergman's Spinning Charged Ring Model of
Elementary Particles (a refinement of Parson's Magneton). The Lucas
Model of the Atom is by far the most successful of all models of the
atom ever proposed. It is a physical model that shows where electrons
are located throughout the volume of the atoms. This model predicts the
"magic numbers" 2, 8, 18, and 32 of electrons in the filled shells and
also is able to predict why the Periodic Table of the Elements has
exactly seven rows. The Lucas model also predicts the structure of the
nucleus and correctly predicts hundreds of nuclide spins.
Earliest Model of the Atom?
The first chapter of Ezekiel’s book found in the Bible seems to
describe rings in a way that is consistent with the most general
features of atomic structure. The four rings described by Ezekiel have
the same physical arrangement and orientations as the rings found in
the Lucas model of the atom. The most important feature of the atom is
its stability, a feature emphasized by Ezekiel for his rings. The
hydrogen gas molecule consisting of two electrons and two protons is
the most simple and abundant form of matter in the universe; and in the
Lucas model, diatomic hydrogen gas “looks” just like the
four rings described by Ezekiel.