Question

What is the atomic theory proposed by John Dalton? What changes have taken place in the theory during the last two centuries?

Answer 1

Sir Jhon Dalton proposed the atomic theory which contains the following postulates:

• Matter consists of indivisible atoms.

• All the atoms of a given element have  similar properties including similar mass. Atoms of different elements have different  mass.

• New compounds are formed when atoms of different ratio combine together in a fixed ratio.

• Chemical reactions that occur involves reorganization of the atoms. These atoms are neither destroyed nor created.

• Sir Jhon Dalton proposed these theories in 1808.

Changes that have taken place in the theory during the last two centuries:

• The changes that has happened to this theory is that atoms can be destroyed with the help of nuclear reactions.

• We have found different kinds of atoms with different atomic mass. Isotopes prove this theory.

Answer 2

Hey......!!!

• All matter is made of atom and atoms are indestructible.

• An atom of an element is identical in mass and property.

• Compounds are formed by the combination of two or more atoms.

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