Question

State and explain Dalton’s atomic theory.

Answer 1

Hint: Dalton’s atomic theory was the first theory which attempted to explain all matter in terms of atoms and their properties. It was a scientific theory on the nature of matter put forward by the British physicist and chemist John Dalton in the year 1808.

Complete step by step answer:
Matter has been one of the most important subjects of research for the science enthusiasts. Scientists have always tried to simplify things and so was the case with matter. They were interested to know about the simpler particles of matter that make up matter and their structure. This led to the formation of many atomic theories.

Democritus was the first man who proposed that all particles are made up of atoms. The theory of Democritus held that everything is composed of "atoms", which are physically, but not geometrically indivisible and that between atoms, there lies empty space and the atoms are indestructible.

After almost two thousand years, John Dalton published his theory in 1808. Dalton based his theory on the law of conservation of mass and the law of constant composition. The main postulates of the theory are:
a) All matter is made up of tiny, indivisible particles called atoms.
b) All atoms of a specific element are identical in mass, size, and other properties. However, atoms of different elements exhibit different properties and vary in size and mass.
c) Atoms can neither be created nor destroyed. Also, atoms cannot be divided into smaller particles.
d) Atoms of different elements can combine with each other in fixed ratios to form compounds.
e) A chemical reaction is a rearrangement of atoms.

Note: Remember that in a chemical reaction, the total mass remains conserved. However, this is not the case in nuclear reactions in which mass is converted into energy.