Page 2 - 2.LESSON NOTES-INTRODUCTION OF THE CHAPTER AND MIND MAP

The postulates of the atomic theory by John Dalton
• The matter is made up of tiny particles called Atoms that cannot be divided.
• Atoms are never formed or destroyed during a chemical reaction.
• Atoms of an element exhibit same nature. They have the same size, mass, and
character.
• Atoms of different elements exhibit variant nature. They do not have same
characteristics.
• Atoms form compounds by combining in a ratio of whole numbers.

 A compound contains a constant number and kinds of atoms
Dalton suggested that atoms can neither be created nor destroyed and are indivisible.
But the discovery of electrons and protons in atoms lead to failure of this aspect of
Dalton’s theory.
Introduction:
Dalton’s atomic theory in suggested that an atom was indivisible. However, the discovery
of two fundamental particles named as electrons and protons, inside the atom, led to the
failure of Dalton’s atomic theory.

Fundamental particles of an atom:
Three particles; electron, proton and neutron from which an atom is consisted of, are
called fundamental particles of an atom or sub atomic particles.

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