he had no idea what an atom was really like. – Dalton did not attempt to describe the structure or composition of atoms. – The second hypothesis states that atoms of one element are different from atoms of all other elements. – Dalton’s concept of an atom was far more detailed and specific than Democritus’. ![]() – The Figure above is a schematic representation of hypotheses 2 and 3. – In this case, the ratio of the atoms of element X to the atoms of element Y is 2:1. (b) Compounds formed from atoms of elements X and Y. (a) According to Dalton’s atomic theory, atoms of the same element are identical, but atoms of one element are different from atoms of other elements. – it does not result in their creation or destruction. (4) A chemical reaction involves only the separation, combination, or rearrangement of atoms. – In any compound, the ratio of the number of atoms of any two of the elements present is either an integer or a simple fraction. (3) Compounds are composed of atoms of more than one element. – The atoms of one element are different from the atoms of all other elements. (2)All atoms of a given element are identical, having the same size, mass, and chemical properties. (1) Elements are composed of extremely small particles, called atoms. – The hypotheses about the nature of matter on which Dalton’s atomic theory is based can be summarized as: – Dalton’s work marked the beginning of the modern era of chemistry. Dalton was the first person to recognize a workable distinction between the ultimate particle of an element (atom) and that of a compound (molecule).– It was in 1808 that an English scientist and schoolteacher, John Dalton, formulated a precise definition of the indivisible building blocks of matter that we call atoms.It has enabled us to explain the laws of chemical combination. ![]() The difference in properties of charcoal, graphite, diamond went unexplained in spite of being made up of same kind of atoms. The theory completely fails to explain the existence of allotropes.This is not seen in complex organic compounds like sugar C 1 2 H 2 2 O 1 1. According to Dalton atoms of different elements combine in simple whole number ratio to form compounds.Such atoms of different elements that have the same atomic mass are called isobar. This has been proved wrong in certain cases like argon and calcium atoms, which have the same atomic mass of 40. Dalton also said atoms of different elements are different in all respects.For example, chlorine has two isotopes having mass numbers 35 a.m.u and 37 a.m.u. Such atoms of the same element having different masses are called isotopes. This is wrong because atoms of some elements vary in their mass and density. ![]()
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