Born in England in 1766 John Dalton was first scientist who laid foundation of atomic theory.
These are actual wood spheres that DALTON used as a model of atom. The are about 200 years old. See the drills in atoms may be used by DALTON to connect atom to other other atom to form compound .
JOHN DALTON , a British scientist was also working in the field of atomic structure for a pretty long time . On the basis of his studies and investigation carried , he came out with a statement that the smallest portion of matter that can not be divided any further is atom . In the year 1808 he gave the famous theory , known as DALTON'S ATOMIC THEORY OF MATTER.
The important postulates of are given below .
1. Every matter is made up of very small particles known as ATOM .
2. Atoms are the ultimate particle of the matter and cannot be further subdivided into smaller particles .
3. Atoms can neither be created nor be destroyed during a physical change or a chemical reaction .
4. All atoms of a particular element are identical in all respect . This means they have same mass , size and chemical properties .
5. Atoms of different element are different from each other . It means they haves different mass , size and chemical properties .
6.Atoms are the smallest particle of the matter that can take part in chemical combinations .
7. Atoms of same or different element combine in small whole number ratio to form molecule of a compound .
LIMITATION OF DALTON'S ATOMIC THEORY
Dalton's atomic theory brought a revolution in the field of chemistry . It was first significant step towards Mordern Chemistry . First time any theory gave concrete information about matter.
However it could not stand for a very long time . Later studied and researches carried by different scientists showed that most of postulates of Dalton's atomic theory are wrong . Some important limitations are given below :
1. Atoms are divisible . They are made up of sub atomic particles like electron , proton and neutron .
2. Atoms of same element may possess different mass. They are called ISOTOPES .
3.Atoms of different elements may possess same mass . They are called ISOBARS .
4. Atoms of different element may not always combine in simple whole number ratio to form molecule of a compound .
SOME IMPORTANT CONCEPTS GIVEN BY DALTON
Atoms of same element have same size and mass .
Dalton also proposed that all atoms of a particular element would be the same size and same mass. Atoms of a element would have unique mass and size .
DALTON'S THEORY WAS BASIS OF LAW OF CONSTANT PROPORTION
Dalton's next idea would tremendously simplify the complexity of matter. Dalton suggested that all substances around us are made up of grouping of specific number of atom of different element . for example water molecule is made up of one atom of oxygen and two atom of hydrogen .
