Introduction

Ancient Indian and Greek philosophers have always wondered about the unknown and unseen form of matter or we can say that what matter is ultimately made up of. It was around 500 BC that an Indian philosopher Maharishi Kanad had postulated that “matter is divisible” i.e. if we go on dividing the matter we will get smaller and smaller particles and ultimately we will get the smallest particle of matter which cannot be divided any further. These indivisible particles were named by him as “Parmanu”.

Around the same era ancient Greek philosopher Democritus and Leuccipus suggested the same idea. However they called the smallest indivisible particles as “atoms” (Greek: means uncutable)

Another Indian philosopher PakudhaKatyayama said that these particles normally exist in a combined form called molecules which give us various forms of matter.

Thus, we may conclude that matter is made up of small particles which may be atoms or molecules. Different kinds of atoms and molecules have different composition that’s why different kinds of matter also show different properties.

Till eighteenth century there were no experimental work done to validate these philosophical ideas. By the end of eighteenth century, the fact had been established that pure substances can be either elements or compounds. Scientist became interested in finding out why and how elements combine and what happens when they combine?