Dalton’s Atomic Theory

Dalton’s Atomic Theory


1 Answers

Sachin Tyagi
31 Points
14 years ago

Dalton’s Atomic Theory:- The concept that matter is composed of very small particles was given by Indian and Greek philosopher. As early as 400 to 500 B.C. the Greek philosopher Democritus suggested that matter cannot be forever divided into smaller and smaller parts. The ultimate particles were called atoms. The word atom has been derived from the Greek word “atomos” meaning indivisible. These early ideas, however, were not based on experiments but were mere speculations. The existence of atoms was accepted by Boyle in his book “The Sceptical Chymist” (1661) and by Newton in his books “Principia” and “Opticks” 1704. The old ideas were put on a scientific scale by John Dalton n the years 1803 to 1808 in the form of a theory known as Dalton’s Atomic Theory which is a landmark in the history of chemistry. The main points of Dalton’s atomic theory are:-

(i)          Elements consist of minute, indivisible, indestructible particles called atoms.

(ii)         Atoms of an element are identical to each other. They have the same mass and size.

(iii)        Atoms of different elements differ in properties and have different masses and sizes.

(iv)       Compounds are formed when atoms of different elements combine with each other in simple numerical ratios such as one-to-one, two-to two, three-to-three and so on.

(v)         Atoms cannot be created, destroyed or transformed into atoms of other elements.

(vi)       The relative numbers and kind of atoms are always the same in given compound.


The theory convincingly explained the various laws of chemical combination, but the theory has undergone a complete shake up with the modern concept of structure of atom. However, the Daltonian atom still retains its significance as the unit participating in chemical reactions. The following are the modified views regarding Dalton’s atomic theory.

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