CHEMISTRY ASSIGNMENT
Published on Mar 06, 2022
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TOPIC- DALTON'S ATOMIC THEORY
- WHO IS JOHN DALTON?
- WHAT IS DALTON'S ATOMIC THEORY?
- POSTULATES OF DALTON'S ATOMIC THEORY
- LIMITATIONS OF DALTON'S ATOMIC THEORY
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John Dalton FRS(6 sept 1766-27 july 1844)was an english chemist,meteorologist and physicist.he is best known for his pioneering work in the development of modern atomic theory,and his research into color blindness(sometimes referred to as daltonism,in his honour) .
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WHAT IS DALTON'S ATOMIC THEORY?
- It was in the early 1800s that john dalton, an observor of weather and discoverer of color blindness among other things ,came up with his atomic theory.
- the idea of atoms had been proposed much earlier.the ancient greek philosophers had talked about atoms,but dalton's theory was different in that it had the weight of careful chemical measurements behind it. It was not just a philosophical statement that there are atoms because there must be atoms.
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POSTULATES OF DALTON'S ATOMIC THEORY
- The postulates of dalton's atomic theory were used to explain the earlier observations of the behaviour of matter.
- Although two centuries old,dalton's atomic theory remains valid in modern chemical thought.
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POSTULATE 1
Matter is composed of very tiny or microscopic particles called atoms
POSTULATE 2
- Atom is an indivisible particle.
POSTULATE 3
- Atom can neither be created nor be destroyed
POSTULATE 4
- atom of an element are identical in shape,size,mass and in other prperties.
POSTULATE 5
- Atoms of different elements are different in their properties.
POSTULATE 6
- Atoms combine with each other in small whole numbers.
POSTULATE 7
- All chemical reactions are due to combination or separation of atoms.
LIMITATIONS OF DALTON'S ATOMIC THEORY
- With the discovery of sub-atomic particles,e.g.,electrons,neutrons and protons,the atom can no longer be considered indivisible.
- The atoms of same elemnts are not similar in all respect.they may vary in mass and density.These are known as isotopes.For example,chlorine has two isotopes having mass numbers 35 a.m.u. and 37 a.m.u.
LIMITATIONS OF DALTON'S ATOMIC THEORY
- Atoms of different elements are not different in all respects.atoms of different elements that have the same atomic mass are called isobar.
- Different elements combine in simple whole number ratio to form compounds.this is not seen in complex organic compounds like sugar .
- This theory fails to explain the existence of allotropes.
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PRESENTED BY ARNAB HALDER
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