A Brief History of Atomic Theory

 — DrTony @ 2:50 pm    Thanks to you Tony!
The Scriptures for this Sunday, the 2nd Sunday of Easter, are Acts 2: 14, 22 – 32; 1 Peter 1: 3 – 9; and John 20: 19 – 31. My post is tentatively entitled “Faith and Vision”. But some of what I want to say or write for Sunday requires an understanding of what we know about the atom and I didn’t feel like putting a theory of the atom into a Sunday piece. Of course, if I were to get called to preach somewhere this Sunday, I would have to figure out a way to condense this.

Should people in the pews have some understanding of the basic principles of physics, chemistry, and biology? Should a pastor or a lay speaker focus on scientific theory when speaking of the Gospel or other passages in the Scriptures?

One would think that the answer to the first question should be yes, if for no other reason than such information is covered in basic courses taught in high school and college. You know that there is a problem when many people still hold onto the Aristotelian view point that heavier things fall faster than light while they were taught in school that all things fall at the same rate. Perhaps I shouldn’t worry but there is other evidence to suggest that there are quite a few basic ideas that are taught in school today but not really learned. And the same applies to church as well; it is well documented that the majority of Americans claime to be Christian but cannot provide basic information about the Bible, Christianity or their denomination.

Clearly, there is a need to reform our educational processes, both in the sectarian schools and in the secular schools as well. And that is one issue that I want to address. But in the meantime, let me offer these thoughts on atomic theory.

To understand the history of atomic theory, you need a basic understanding of the processes of science. Some of this was covered in “Processes of Science”; I may expand on that later.

The simplest way to start is to say that the “universe” is composed of matter and energy. As a consequence of Albert Einstein’s work on relativity, we know that matter and energy are interchangeable.

Generally speaking, we break down matter from heterogeneous mixtures into homogeneous mixtures (or solutions) and then into compounds and elements. The separation of mixtures is done mainly through physical changes and processes. The separation of compounds into elements is done through chemical changes and processes. (See “Matter Chart” for a pictorial explanation of this.)

Elements are the simple form of matter and atoms are the simplest form of an element. The Greek philosopher/scientist Leucippus and his student, Democritus, developed the first atomic theory in the 5th and 4th century (B.C.E.). The word “atom” is derived from the Greek for “indivisible” and the premise of the theory was that atoms were indivisible particles. The theory that Democritus developed from his studies with Leucippus was not easily accepted at the time and there are suggestions that Democritus’ works were destroyed or people were discouraged from using them.

But Issac Newton would find references to these works and use them developing his ideas on optics. (In the preparation of these notes, I found a reference that said that Newton believed the idea of atoms was first developed by a person known as Moschus or Moses of Sidon; Newton believed this to be the biblical Moses – references: http://plato.stanford.edu/entries/atomism-ancient/ and http://en.wikipedia.org/wiki/Democritus. The foundation for this linkage may be more theological in nature but if you understand Newton, this is totally understandable – see “A Dialogue of Science and Faith”.) Other contemporaries of Newton’s, including Robert Boyle and John Dalton, would use the idea of the indivisible particle to explain some of their observations.

Dalton would codify his thoughts in what we called the first modern atomic theory. All matter consists of tiny particles called atoms that are indestructible and unchangeable. Elements are characterized by the mass of their atoms. When elements react, their atoms combine in simple whole-number ratios; though sometimes there may be more than one possible ratio.

Dalton also included a postulate that when atoms combine in only one ratio, it is a binary one, unless some cause appears to the contrary. Now, Dalton had no experimental evidence to support this postulate and it led him to assume that the formula for water was OH and the formula for ammonia was NH. This in turn lead him to incorrectly determine the mass of oxygen and nitrogen. These incorrect values would lead to conclusions that were not supported by the experimental data and would prevent many from accepting his theory. (A Short History of Chemistry, J. R. Partington, MacMillan (London), 1937)

In the end, his basic statements about the nature of the atom, though modified, are still true today.

Now, if science is absolute, which some people believe to be the case, then the activities of the18th and 19th century will cause them grief. In addition, if one is not able to see the connection between two sets of data, it is also possible that what happened in the 18th and 19th century will also cause them grief.

It may be true today that what transpires in chemistry today often times has little impact on what is happening in physics or biology. And it also may be true that there are many chemists, physicists, and biologists who have no interest in what transpires in the other fields. And we certainly teach these subjects as if they were independent of each other. But that was certainly not the case in the 18th, 19th, and early 20th centuries.

The discovery of electricity would lead to the discovery of the electron and suggest that the atom was, in point of fact, divisible. And because the electron carried a negative charge (although this was an arbitrary decision), it implied the existence of a second charged particle which was ultimately called the proton.

The discovery of radioactivity also brought into doubt the stability of the atom. Wilhelm Röentgen’s discovery of X-rays would lead others to seek other sources of radiation (though, as I pointed out in “The Strange Case of Mr. Piltdown”, not with the same results). In 1896 Henri Becquerel, Pierre and Marie Curie would identify and characterize what we call radioactivity (the three would share the 1903 Nobel Prize in Physics).

Ernest Rutherford, working with Paul Villard in 1899 and 1900, characterized radioactivity as alpha (α) and beta (β) rays. A third form of radiation (gamma – γ – rays) would also be discovered. The names of these rays were chosen in order of their discovery. Later experiments would show that these were not alpha and beta rays but particles. A side note – in 1948 George Gamow would suggest to Robert Alpher that Hans Bethe be added as a co-author for their paper on the synthesis of the elements that they (Gamow and Alpher) had been preparing for publication. This paper (Alpher, R. A., H. Bethe and G. Gamow, “The Origin of Chemical Elements,” Physical Review, 73, Issue 7, (1948), 803-804) would provide data and thoughts on how the various elements (from hydrogen to heavy elements such as uranium) were synthesized in the universe. The details in this paper would provide the first suggestion of what we now call the “big bang”. Because of the inclusion of Hans Bethe’s name on the paper, the paper became known as the Alpha – Beta – Gamow paper and because it was published on 1 April 1948, it was seen more as a joke or an attempt at humor than real and ground breaking physics.

With the discovery of radioactivity and the knowledge that some atoms emitted alpha and/or beta particles, the notion that the atom was indivisible and indestructible was pretty well destroyed. This discovery would also lead to the discovery of isotopes, atoms of the same element but with different masses. This was obviously in clear violation of one of John Dalton’s postulates that all atoms of the same element have the same mass.

Isotopes are atoms of the same element with different masses. This discovery meant that further study of the atom was necessary. It required the refinement of the atomic theory and an explanation for the makeup of isotopes in terms of atomic masses and atomic numbers (for explanation of isotopes from the 1930′s, see “Thoughts on the Nature of Teaching Science in the 21st Century”; this explanation was in print at the same time as the discovery and confirmation of the existence of the neutron).

In addition, the idea that some nuclei of atoms (the nucleus was first identified by Rutherford while working on and with alpha and beta particles) were unstable lead to experiments which resulted in the splitting of the atom (nuclear fission, first proposed by Enrico Fermi and Leo Szilard in 1993 and confirmed by Lise Meitner, Otto Frisch, Otto Hahn, and Fritz Strassman in 1939).

This work would ultimately lead to the development of the atomic bomb but it would also open the door to the creation of man-made elements and an understanding of nuclear decay and ½-life.

Decay in this context is meant to describe the physical and chemical breakdown of an unstable atom by the emitting of one type of particle; ½-life is the time it takes for ½ of the material to decay. These terms can and are equally applicable to other materials such as plastics. One reason for recycling plastics is because the ½-life of many plastics is extremely long and unless the material is biodegradable, unlikely to decay in a land-fill somewhere.

The discovery of the neutron doesn’t mean that the development of the atomic theory is complete. Further work has shown that protons, neutrons, and electrons can be further subdivided. Each step in this process is increasingly more complex. But complexity does not preclude solvability and the work goes on.

At this point, one can see that the postulates first proposed by Dalton are no longer valid as written. The idea that the atom is indivisible has been replaced with the notion that there are some other basic particles which cannot be divided. And physicists are working on that idea as this piece is being written. Perhaps one day there will be an ultimate atomic theory – that is what Democritus was seeking and what Dalton was seeking and what drives the exploration of the world of sub-atomic particles today.

Fortunately, for most chemists, the atomic theory of the proton and neutron in the nucleus and electrons in “clouds” around the nucleus provides a nice working model that explains most, if not all, chemical reactions.

Similarly, the idea of nuclear decay and ½-life become very useful in other areas of science; areas perhaps where the collisions of faith, logic, reason and belief collide.

In the next part of this discussion, I want to look at the measurement of the age of something.