This document provides an overview of the historical development of atomic theory. It discusses early Indian philosophers like Maharishi Kanad and Pakudha Katyayama who postulated that matter is made of small particles. Later, Greek philosophers Democritus and Leucippus suggested the idea of atoms as indivisible particles. Antoine Lavoisier established the laws of conservation of mass and constant proportions through experiments. John Dalton provided further explanation through his atomic theory, stating that all matter is made of atoms that combine in whole number ratios to form compounds.

1. ATOMS AND
MOLECULES
LECTURE-1
CHEMISTRY
BY: MISS RITIMA
( YOU TUBE CHANNEL : SHORT SHOT BIOLOGY
FOLLOW @ SLIDE SHARE APP- MISS RITIMABIOLOGYEXP)

2. MAHARISHI KANAD
HE POSTULATED THAT IF WE
KEEP ON DIVIDING THE MATTER
(CALLED AS ‘PADARTH’) WE WILL
GET SMALLER AND SMALLER
PARTICLES. AND SOON WE WILL
ACHIEVE THE SMALLEST OF
PARTICLES (CALLED AS
‘PARMANU’) WHICH MAY NOT
DIVIDE FURTHER.

3. PAKUDHA KATYAYAMA
HE POSTULATED THAT THERE
ARE VARIOUS FORMS OF MATTER
BECAUSE THE PARTICLES OF
MATTER EXIST TOGETHER IN
COMBINATIONS.

4. THE IDEA OF DIVISIBILITY
BY GREEK PHILOSOPHERS
DEMOCRITUS AND LEUCIPPUS
• THEY SUGGESTED THAT WHEN WE KEEP ON
DIVIDING THE MATTER THERE COMES A
TIME WHEN NO MORE DIVISION OF
PARTICLES CAN TAKE PLACE. SUCH
PARTICLES ARE CALLED ATOMS WHICH
MEANS BEING INVISIBLE.
• BUT ALL THESE IDEAS WERE NOT BACKED
UP BY MANY EXPERIMENTAL PIECES OF
EVIDENCE UNTIL ANTOINE L. LAVOISIER
PROVIDED TWO LAWS OF CHEMICAL
COMBINATION.

5. LAWS OF CHEMICAL
COMBINATION
• ANTOINE L. LAVOISIER LAID THE
FOUNDATION OF CHEMICAL
SCIENCES BY ESTABLISHING
TWO IMPORTANT LAWS OF
CHEMICAL COMBINATION.
a. LAW OF CONSERVATION OF
MASS
b. LAW OF CONSTANT
PROPORTIONS

6. LAW OF CONSERVATION OF
MASS
• LAW OF CONSERVATION OF
MASS STATES THAT MASS CAN
NEITHER BE CREATED NOR BE
DESTROYED IN A CHEMICAL
REACTION.
• IN A CHEMICAL REACTION THE
MASS OF REACTANT IS EQUAL TO
THE MASS OF PRODUCT.

7. LAW OF CONSTANT
PROPORTIONS
• THIS LAW WAS STATED BY
PROUST.
• IT STATES THAT IN A CHEMICAL
SUBSTANCE THE ELEMENTS ARE
ALWAYS PRESENT IN THE
DEFINITE PROPORTION BY MASS.

8. BUT STILL THERE WAS A PROBLEM
FACED BY SCIENTISTS REGARDING
APPROPRIATE EXPLAINATION OF
THESE LAWS. THEN BRITISH CHEMIST
PROVIDE BASIC THEORY ABOUT THE
NATURE OF MATTER.
HIS THEORY IS BASED ON THE LAWS
OF CHEMICAL COMBINATION .
DALTONS ATOMIC THEORY PROVIDED
N EXPLAINATION FOR LAW OF
CONSERVATION OF MASS AN LAW OF
CONTANT PROPORTIONS.

9. DALTONS ATOMIC THEORY
• ALL MATTER ARE MADE UP OF VERY TINY
PARTICLES CALLED ATOMS.
• ATOMS ARE INDIVISIBLE PARTICLES
WHICH CAN NOT BE CREATED OR
DISTROYED IN A CHEMICAL REACTION.
• ATOMS OF GIVEN ELEMENTS ARE
IDENTICAL IN MASS AND CHEMICAL
PROPERTIES.
• ATOMS OF DIFFERENT ELEMENTS HAVE
DIFFERENT MSSES AND CHEMICAL
PROPERTIES.
• ATOMS COMBINE IN THE RATIO OF SMALL
WHOLE NUMBERS TO FORM COMPOUND.
• THE RELATIVE NUMBER AND KINDS OF
ATOMS ARE CONSTANT IN A GIVEN
COMPOUND.

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