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Early ideas of Democritus and Dalton

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Dalton's Atomic Theory vs. The Hypotheses of Democritus

By Mollie B, Steve H, and Anna M


John Dalton







In its original wording, Dalton’s Atomic Theory states that “matter consists of individual atoms as irreducible units of Boyle’s elements, that each atom of a given element has identical attributes, that differences among elements are due to fundamental differences among their constituent atoms, that chemical reactions proceed by simple rearrangement of indestructible atoms, and that chemical compounds consist of molecules which are reasonably stable aggregates of such indestructible atoms” (“Atomic Structure and Spectra” 371 - 372). In layman’s terms, his theory states that matter cannot be indefinitely subdivided because elements are made up of atoms. Atoms of the same element have the same mass, volume, and chemical properties, whereas atoms of a different element have different properties. It states that elements can chemically combine to create compound atoms, and also that chemical reactions are the separation, joining, or rearrangement of atoms. Atoms of one atom can never be changed into another element (“Atoms” 108).


John Dalton was born on September 6th, 1766 and he died on July 27th, 1844. He was a British chemist and physicist who is known for developing the atomic theory of matter. Dalton was always very smart and at the age of twelve he took over a Quaker school in Cumberland, England. When he was fourteen, he taught his brother in Kendal and continued to teach there for another twelve years. In 1800 he stopped teaching and worked as a secretary at the Manchester Literary and Philosophical Society. Although Dalton was no longer employed by a school, he continued to teach for most of his life. Dalton was also very interested in meteorology and astronomy. He also designated much of his life to researching the trait of color blindness because it was something both he and his brother suffered from. Dalton had a very fulfilling seventy-eight years of life. (“Biography of John Dalton”)


Dalton based all of his evidence on experiments. In 1803 while Dalton was experimenting, he noticed that if he combined oxygen and carbon, they formed two different compounds. He also noted that he had to have fixed ratios. This was a major experiment that lead to the formation of his atomic theory. Dalton was also very careful in his measurements and made sure each was exact and noted so that they could be repeated and justified. (“Biography of John Dalton”)


Democritus (460-370 BCE) was also an interesting scientist. He was often called the “laughing philosopher,” and was noted to always have a smile in public. Democritus lived to be over 100 years old. He spent his days and nights studying and attempting to learn more about the world around him. Democritus didn’t believe in elements. He believed that an infinite number of indestructable atoms existed. He did not believe that phase change was possible. Democritus' complete lack of experimentation led him to the conclusion that matter was in certain phases because of the shape of its atoms. The majority of his "theories" were based on the teachings of Leucippus, his mentor.


Democritus had theorized earlier that “matter is subdivided into discrete building blocks called atoms, which are not divisible any further” (“Atomic Structure and Spectra” 371). They were both essentially correct, but Dalton was able to back up his conclusions with scientific evidence and experimental testing, whereas Democritus’ hypothesizing was a product of his mind with no scientific basis. We now define an atom as the smallest particle of an element that retains the properties of that element (“Atoms” 108).





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