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Democritus
First one to suggest atoms exist and said they are indestructible and indivisible which led to others trying to prove him wrong and further discoveries -
Robert Boyle
Built the air pump with Robert Hooke to help his experiments for air combustion, animal breathing and transition of sound -
Antoine Lavoiser
Came up with law of conservation; matter can’t be made nor destroyed -
John Dalton
He discovered that certain gases could only be combined in certain proportions, even if two different compounds shared the same common element or group of elements -
Dimitri Mendelev
Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law -
Eugen Goldstein
Used a CRT to experimentally determine the charge to mass ratio of an electron -
J.J. Thomson
Discovered the electron while experimenting with a cathode ray -
Max Planck
Created the quantum theory of energy which helped undertand atomic and subatomic processes -
Robert Millikan
Oil mass experiment determined the charge and the mass of an electron -
Ernest Rutherford
Used alpha particles as atomic bullets. Established that the nucleus was very dense, very small and positively charged -
Niels Bohr
Said the atom was a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus -
Henry Moseley
Discovered relation between wavelengths and atomic number -
Erwin Schrodinger
Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom -
James Chadwick
Discovered the neutron