Dalton's Atomic Theory
The theory that 'all matter is made up of very tiny indivisible particles (atoms)' is called atomic theory of matter.Dalton put forward his atomic theory of matter in 1808.The various postulates (or assumptions) of Dalton's atomic theory of matter are as follows :
1.All the matter is made up of very small particles called 'atoms'.
2.Atoms cannot be divided.
3.Atoms can neither be created nor destroyed.
4.Atoms are of various kinds. There are as many kinds of atoms as are elements.
5.All the atoms of a given element are identical in every respect, having the same mass,size and chemical properties.
6.Atoms of different elements differ in mass, size and chemical properties.
7.Chemical combination between two (or more) elements consists in the joining together of atoms of these elements to form molecules of compounds.
8.The 'number' and 'kind' of atoms in a given compound is fixed.
9.During chemical combination,atoms of different elements combine in smaU whole numbers to form compounds.
10.Atoms of the same elements can combine in more than one ratio to form more than one compound.
Dalton's atomic theory was based on the laws of chemical combination. For example,the postulate of Dalton's atomic theory that 'atoms can neither be created nor destroyed' was the result of law of conservation of mass given by Lavoisier.And the postulates of Dalton's atomic theory that 'the elements consist of atoms having fixed mass, and that the number and kind of atoms in a given compound is fixed',came from the law of constant proportions given by Proust.
Dalton's atomic theory was the first modem attempt to describe the behaviour of matter (or properties of matter) in terms of atoms. This theory was also used to explain the laws of chemical combination in terms of atoms. Dalton's atomic theory provides a simple explanation for the laws of chemical combination.
(a) The postulates of Dalton's atomic theory that 'the elements consist of atoms and that atoms can neither be created nor destroyed' can be used to explain the law of conservation of mass.
(b) The postulates of Dalton's atomic theory that 'the elements consist of atoms having fixed mass,and that the number and kind of atoms of each element in a given compound is fixed" can be used to explain the law of constant proportions.
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Atoms and Molecules - Notes
2. Monovalent Cations (Cations Having a Valency of 1+)
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3. Divalent Cations (Cations Having a Valency of 2+)
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4. Trivalent Cations (Cations Having a Valency of 3+)
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6. an example, let us give the significance of symbol C
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7. Formulae of Some Molecular Compounds
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9. Molecular Formulae of Some Common Elements
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10. Explanation of the Law of Conservation of Mass
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11. 2. A Negatively Charged Ion is Known as Anion
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13. As an example, let us give the significance of the formula H
2O
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14. Simple Ions and Compound Ions (Polyatomic Ions)
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21. Gram Atomic Mass And Gram Molecular Mass
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28. 1. A Positively Charged Ion is Known as Cation
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34. Divalent Anions (Anions Having a Valency of 2-)
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35. Molecular Masses of Some Common Elements
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37. Explanation of the Law of Constant Proportions
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39. Significance of the Formula of a Substance
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42. Symbols Derived from Latin Names of the Elements
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45. Valencies of Some Common Metal Elements Valencies of Some Common Non-Metal Elements
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46. Atomic Masses of Some Common Elements
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47. Writing Of Formulae Of Molecular Compounds
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50. Writing Of Formulae Of Ionic Compounds
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