Any piece of matter can be divided into smaller parts and each part can be subdivided into smaller parts which can't be divided this part is called Atom.
a-He refused the idea of Greek philosophers about the atom .
b- He supposed that all matters composed of 4 constituents which are ( water, air ,dusta and fire and postulated that the cheap metals such as iron or copper can be changed into precious ones like gold by changing the percentage of fourconstituents.
3- Boyl ( lrish 1661 )
i-He refused the Aristotle concept.
ii-He was the 1st scientist to define the element as pure simple substance which can
not be analvsed into smple one by normal chemical methods.
4) Dulton s atom ( Englsh 1803 )
He supposed thet :
<!--[if !supportLists]-->1-The substance consists of very amall particles called atoms.<!--[endif]-->
<!--[if !supportLists]-->2-Every element consists of very small dense atoms which can t be divided.<!--[endif]-->
<!--[if !supportLists]-->3-Atoms f the same element are identical.<!--[endif]-->
<!--[if !supportLists]-->4-Atome of different are different.<!--[endif]-->
N.BBy the 19 th century
Scientists had accepted the idea that elements consists of atoms but they knew very little about those atoms.