Dalton's Atomic Theory—(Chemistry)

Dalton's Atomic Theory
The theory that' all matter is made up of very tiny indivisible particles (atoms)' is called atomic theory of matter. Dalton's put forward his Atomic Theory of matter in 1808. The various postulates of Dalton's atoAto Theory of matter are as follows:

• All the matter is made up of very small particles called 'atoms'.
• Atoms cannot be divided.
• Atoms can neither be created nor destroyed
• Atoms are of various kinds. There are as many kinds of atoms as are elements.
• All the atoms of a given element are identical in every respect, having the same mass, size and chemical properties.
• Atoms of different elements differ in mass, size and chemical properties.
• Chemical combination between two elements consists in the joining together of atoms of these elements to form molecules of compounds.

Drawbacks of Dalton's Atomic Theory
It is now known that some of the statements of Dalton's Atomic Theory of matter are not exactly correct. Some of the drawbacks of the Dalton's Atomic Theory of matter are given below:

1. One of the major drawbacks of Dalton's atomic theory of matter is that atoms were thought to be indivisible (which cannot be divided). We now that under special circumstances, atoms can be further divided into still smaller particles called electrons, protons and neutrons. So, atoms are themselves made up of three particles: electrons, protons and neutrons.
2. Dalton's atomic theory says that all the atoms of an element have exactly the same mass. It is, however, now known that atoms of the same elements can have slightly different masses.
3. Dalton's Atomic Theory said that atoms of different elements have different masses. It is, however, now known that ever atoms of different elements can have the same mass.