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Dalton's Atomic Theory


This theory, which was first put forward in 1808 by John Dalton, is regarded as the foundation of modern chemistry. It gave insight into the composition of matter, and explained many chemical phenomena that were not understood before then. In summary, the theory consists of the following ideas:

1. That matter is made up of small, indivisible, discrete particles called atoms.

2. That atoms are indestructible, and cannot be created.

3. That atoms of a particular element are all exactly the same in every respect, and are different from those of all other elements. This explained why elements are pure substances, with each element having the same properties that are different from other elements.  

4. That chemical combination occurs between small whole numbers of atoms of the reacting substances. This explained chemical reactions and the properties of the new substances formed.

Dalton’s atomic theory stood for about a century and became the basis for studying chemical composition and reaction. However, as fresh knowledge became available over the decades some incorrectness was noticed in the theory.   

These include the statement that atoms are indestructible and cannot be created. That claim has been found not to be completely true with the discovery of nuclear chemistry where nuclear reactions could destroy and create different atoms.

However, it is worthy to note that it is only through nuclear reactions that you can have atoms being destroyed or created, it does not happen in chemical reactions. So Dalton’s atomic theory as regards chemical reactions still hold true.

Another area where Dalton’s theory has been faulted is in stating that atoms of the same element are exactly alike in all respect. The discovery of isotopes in some elements where there are atoms of different masses has made that statement not to be totally correct.

In spite of the incorrectness in some aspects of Dalton’s atomic theory, the explanation that chemical reaction involves the separation and combination of atoms, and that these atoms possess characteristic properties has remained relevant in today’s study of chemistry.

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