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450 BCE
Aristotle
He created the scientific method of analysis, he get the credit with categorizing fields of knowledge such as psychology, biology, politics, logic, chemistry, and botany. -
450 BCE
Democritus
All matter around us is made of indivisible tiny particles- “atomos” -
Antoine Lavoisier
He is considered father of modern chemistry, thanks to his discovery of the conservation of matter. -
John Dalton
Created Dalton's Atomic Theory
Dalton’s Atomic Theory
1) Elements are made of tiny particles called atoms.
2) Atoms of one element are identical while atoms of different elements are different.
3) Conservation of atoms
4) Different atoms form compounds in constant ratios. -
Dmitri Mendeleev
He created the periodic table by arranging the chemical elements in order of their atomic weights and recording their symbols -
J. J. Thomson
Discovered atoms have negative particles; electrons. He also discovered electron’s charge to mass ratio
1.76 x 108 C/g -
Robert Millikan
Measured the charge of an electron.
Electron’s charge: 1.60x 10-19 C
Electron’s mass: 9.11 x 10-28 g -
Ernest Rutherford
Positive charge is not like a pudding, but concentrated in the nucleus as shown in the Gold Foil -
Niels Bohr
He discovered Bohr's Orbit model
*Electrons orbit the nucleus.
*Model based on the hydrogen atom
*Energy of the electrons is quantized. -
James Chadwick
He discovered the neutron, his discovery led to the splitting of Uranium-235 and ultimately to the development of the first atomic bomb -