John Dalton :
He was born in poor weaver's family in 1766 in England. He began his career as teacher at the age of twelve.
Seven years later he become a school principal. in 1793, dalton left for Manchestar to teach mathematics, physics and chemistry in a college.
He spent most of his life there teaching and reseraching. In 1808, he presented his atomic theory which was a turning point in the study of matter.
Dalton Atomic Theory :
1- All Matter is made of very tiny particles called atoms, which made the existense of chemical reaction.
2- Atoms are indivisible particles, which cannot be created nor destroy in a chemical reaction.
3- Atoms of given element are identical in mass and chemical properties.
4- Atoms of different element have different chemical properties and masses.
5- Atoms combine in the ratio of small whole number to form compounds.
6- The relative number and kinds of atoms are constant in a given compound.
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