Dalton’s Atomic Theory
Dalton’s atomic theory and the development of the periodic table in Mendeleev in 1869 led to the rapid growth of chemistry as a science. In particular, the influence of the location and number of electrons in atoms on the properties of elements has become one of the essential ideas of chemistry.
Ever since our existence on this planet, the human brain has been curious to understand nature. This curiosity has been the mother of all inventions. The matter has been one of the most important subjects of research for science enthusiasts.
Scientists and philosophers have always tried to simplify things and so was the case with the matter. They wanted to know about the fundamental particles that make matter, their properties, structure etc. This led to the formulation of a number of atomic theories.
Democritus was the first man to propose that matter is made up of particles called an atomos meaning indivisible. This was then referred to as Democritus’ Atomic Theory. Due to the lack of technological set up back then, information based on this theory was very limited.
Almost after two millennia, the works on the simplifying matter was materialized by Dalton. In 1808 John Dalton postulated the famous Dalton’s Atomic Theory. He published this theory in a paper titled “A New Chemical Philosophy”; indeed the philosophy was new for that era.
Postulates of Dalton’s Atomic Theory
The postulates of Dalton’s Atomic Theory were as follows:
- The matter is made up of indivisible particles known as atoms.
- The properties of all the atoms of a given element are same including mass. This can also be stated as all the atoms of an element have identical mass; atoms of different elements have different masses.
- Atoms of different elements combine in fixed ratios to form compounds.
- Atoms are neither created nor destroyed. This implies that during chemical reactions, no atoms are created nor destroyed. The formation of new products (compounds) results from the rearrangement of existing atoms (reactants).
Dalton’s Atomic Theory also suggested that the smallest part of an atom that can take part in a chemical reaction is an atom. Some postulates of this theory remain valid even in modern chemical thoughts. The atomic structure model proposed by Dalton has proved to be a stepping stone in chemistry and forms the base for modern atomic theories and quantum mechanics.
Limitations of Dalton’s Atomic Theory
The main failures of Dalton’s atomic theory are
- It failed to explain how atoms of different elements differ from each other.
- It failed to explain the nature of forces that hold together different atoms in a molecule.
- It failed to explain Gay Lussac’s law of combining volume.
- It could not explain how and why atoms of different elements combine with each other to form compound atoms or molecules.
- It did not explain any distinction between ultimate particle of an element that takes part in reactions and ultimate particle that has an independent existence.
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