Atomic Proposal

The Idea of the atom were first proposed by the Greek philosophers Democritus and Leucippus around 400 B.C. At that time, there is absolutely no real evidence that support this proposal. Even after 20 centuries later, no experiment was strong enough to verify the existence of the atom. 

In the 18th Century, the first scientific data on the atom were gathered by A. L. Lavoisier and others from quantitative measurements of chemical reactions. From the experiment, he suggested that there exist some elements which could not be disintegrated into any smaller composition by usual chemical method. He defined this as chemical element. 

From the results of Lavoisier experiments, John Dalton proposed the first systematic atomic theory. This theory of the atom compose of two basic chemcial laws: the law of constant proportions and the law of multiple proportions. 

Law Of Constant Proportions
"The composition of a pure chemical compound is independent of its method of preparation"

Example: Water is a compound of hydrogen and oxygen. The ratio of the weight of hydrogen to oxygen in water is fixed at the value 1:8, independent of how it is formed. 

Law Of Constant Proportions
"When two elements A and B combine to form more than one compound, the weights of B which combine with a fixed weight of A are in the proportion of small whole numbers (integers)".

Example: Carbon and oxygen react to form CO or CO2 but not CO1.1 or CO1.2.

Carbon Dioxide and Monoxide

Carbon Dioxide and Monoxide

Sources:
1. The discovery of the Atom

4 Responses to “ Atomic Proposal ”

  1. [...] the atomic theory proposed by John Dalton created a basic structure of the atom, the general idea of molecules was [...]

  2. [...] theory of gases. The development of this theory in the 19th century are mostly based on the theory of atoms & molecules. Since there are no real experiments during that time, many leading physicists [...]

  3. I am a school pupil, and I have found this website very useful. Keep up the good work- as I say at school, the Higgs Boson is round the corner!! I have always been interested in Quantum Chemistry.

  4. Top draw!

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