Atomic Structure: Beyond the Discovery of the "Indivisible"

It is a known fact that the smallest unit of matter or of the chemical element is the Atom; However, this was not always the case for all theories originate with an idea. Greek philosopher, Democritus, was the first to provide an atomic theory and therefore give existence to the "atomos," or the indivisible during the fifth century BC. His vision of the atomic model depicted a void or an empty space where the eternal atom lies; one which could continue to be broken down until it is in fact indivisible. His philosophical-based theory went as far as to propose that the atom maintains the unique properties of its original source, distinguished only by size and arrangement of its solid form. Nevertheless, Democritus lacked an accurate explanation of the atoms chemical behavior for it could be further simplified and therefore altered. It would be another 2000 years before his atomic theory was anew developed to fit a more suitable direction towards the uncovering of subatomic particles.

Chemist, John Dalton, developed a more valid description of matter by providing a foundation for the unit's behavior through experiment-based concepts. Today he is recognized for his atomic theory consisting of four significant rules in chemistry. For example, he was capable of foretelling that the atom is unique and distinguished from other atoms of an element for its weight or as presently referred to as atomic mass, by observing the distinct qualities of gas absorption in water as a response to variations in size. Nevertheless, modern chemistry matured to reveal slight differences in mass due to changes in nuclear charge (isotopes). Dalton is often recognized for his reputable contribution to the law of conservation of mass: When atoms of a corresponding element, a substance in its simplest existing structure, combine in whole number ratios with those of different elements to form chemical compounds, mass is neither created nor destroyed but rearranged through association and dissociation of atoms. Furthermore, Dalton's research was essential for understanding interaction between atoms because he not only attempted to categorized the different elements but pinpointed important aspects of atomic behavior when undergoing a chemical reaction.

John Dalton's atomic theory was modeled on the idea that atoms were filled spheres; inaccurate in modern chemistry for the atom is composed of protons, neutron, electrons (subatomic particles) and its center of mass, the nucleus. The discovery of these particles and their charge began with Joseph John Thomson's revelation in his 1987 cathode ray experiment. Furthermore, his experimental model consisted of a cathode ray tube, balanced in charge by a negative and positive conductor at opposite ends. Thomas discovered that the electric charge detected was not separate from the cathode ray itself but rather they were single forms of matter. Nevertheless, he was not able to identify the negative charge as particles until he placed opposing charges within the tube; Thomas observed the cathode ray attract to the positive plate and therefore its negative charge was identified as an essential part of the atom. Although J.J. Thomson's discovery of the electron renewed the atomic structure to depict plums (electrons) embedded in pudding (positive environment), physicist Earnest Rutherford's gold foil experiment opposed such model because it located positive charge in the atoms center (1911).


 By Lupita Sanchez


Article Source: Atomic Structure: Beyond the Discovery of the "Indivisible"