Structure of Atom

Greek philosopher:

All matter can be divided into smaller parts
Each part can be subdivided into smaller parts and further into smaller one and so on until reaching undividable fragment called ATOM which means in Greek language (no divide)

(A) means No

(TOM) means Divide

Aristotle:

Matter composed of 4 elements:

Fire: which is hot and dry
Air is moist and warm
Dust (earth): is dry and cool
Water is cool and moist.

Cheap metals can be changed into precious ones

Robert Boyle: The 1st scientist who defined the element as:

{A pure simple substance which can't be analyzed (or broken down) into simple one by normal chemical methods}

John Dalton:

All element are composed of very small particles called atoms
The atoms can't be divided (indivisible particles)
Atoms of the same element are identical (have the same mass)
Atoms of one kind of element are different from the atoms of all other elements
Compounds are made of molecules and formed by joining atoms in specific whole number ratio