1. Chemist in the Development of an Atom
-> Thales of Miletus(640 B.C. )Founder of Natural Philosophy. He believe that all things comes from water.
-> Democritus of Abdera (460 B.C.)He considered that all matter is made up of tiny discrete indivisible and
indestructible unit of matter called atom.
-> Aristotle (384)He is a greek philosopher rejected the idea of atom but proposed the four element theory
-> John Dalton (1803)English scientist and teacher adopted the idea of democritus. Founded the Daltons
-> Antoine lavoisier (1743)Initiate the law of Conservation of matter. The founder of Modern Chemistry
-> William Crookeshe introduced the Cathode Tube and ray. The tube that shows the flow of electron s in an
electric current and the radiated flow of cathode and anode.
-> Joseph John thomson ( 1856)english physicist discovered electrons and introduce the “Plum Pudding
Model of an Atom”.
-> Robert Millikan (1868) Study the “Oil Drop “ experiment that determines the discharge of an electron.
-> Willihelm RoentgenHe is a german physicist experiemented on cathode ray as well as discovered the x-
-> Antoine Becquerel (1852)He discovered Uranium and participated in radioactivity o f some elements
-> Earnest Rutherford (1871)He discovered proton an descriminate alpha ,beta and gamma radiation. The
man behind alpha –scattering light experiment.
-> James Chadwick (1891)British Physicist. He discovered neutron
-> Max Planck (1858)German physicist. He proved that atoms and molecules absorbed energy only in whole
number in a defined amount called QUANTA.QUANTA is the smallest quantity of energy that can be emitted
or absorbed in the form of electro magnetic radiation..he is responsible to the photo electric effect known as
-> Niels Bohr (1885)danish physicist . He suggested the “Planetary or mini solar system model of an atom”.
-> Louis de Broglie (1924) recommend the wave mechanical model
-> Erwin Schrodenger (1887)He suggested the wave properties and the Quantum Mechanical Model of an
- Quantum Model describes the energy of electron in atom by a number called Quantum Numbers.
- ORBITAL is a region around the nucleus of an atom where an electron with a given energy is likely to be